You can analyze it a number of ways but the key features are the B "pedal" in the melody, the voice leading, and the strong to weak harmonic accents.
Since this is all over a B7 chord all these are B chords.
These are all B13b5#9 chords with the 6th and #9's emphasized. At least that is the sound that you ultimately hear. Depending on how the chords are voiced in the other instrument and such it may or may not work well and the effect you are liking is going to depend on a lot of factors.
You can think of it as simply emphasizing the blue notes of the blues scale.
If you want to be able to play around with such things learn different ways to voice the B13b5#9 chord(there are hundreds of ways) and learn to move between them using smooth voice leading(or not, it's up to you).
Remember, you don't have to play every note in the chord but makes sure the background harmony is a B13 chord or you won't get the effect. e.g., if you just play that harmony by itself you do not get a B13 sound or at least it starts to sound like a progression(e.g., G#m to E9 instead of a coloring of B13).
e.g., the progression can be thought of a G#m E9 E7 E9 (E9 from the minor mode)
Which, if you wanted, you can simply say this is all an E13 chord!! Which means when you learn all your B13 chords they will work over(more or less) the E13 chords and vice versa(among a few others).
So, you can look at the lick as a continuation of the IV7 chord into the I7 chord(a sort of polychord) for the turn around or simply colorations of a B7 chord.
In any case(how ever you look at it) the B pedal, the voice leading, and the Strong/weak stress is what is important. If you copy those properties and change other things you'll be able to get as many variations as you want.
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Ok, realize that you can play "shell" voicings of the chord because they tend to be played by other instruments. Suppose you want the harmony to sound a B13b5#9 and the other instruments are playing a B7 chord. Well B7 = B D# F# A and B13b5#9 = B C# D D# E F F# G# A.
Since we can't play all those notes(and probably don't want to) we can leave out at least the unimportant ones or the ones that clash too much. The notes we need to play because the other instruments are not are the C# D E F and G#. The C#, the maj9th of chord, going to sound a bit dissonant with the D so we'll leave that out. Essentially we are changing the maj9th into a augmented 9th(D to D# or 9th to #9th). This leaves us with the notes D E F G#. Add in the B and you get a complete E9 chord. E9 is the IVth of the key.
So effectively he is playing E9(from the minor mode) over the B7 chord giving a B13b5#9 sonority. He doesn't play the E but on the weak beat because the it and the F(the b5) form a min2nd dissonance which gives that sort of B7sus sound.
The best way to think about it though, IMO, is that he is simply playing the IV chord over the I chord with a pedal on the tonic(which sort of ties it all together). By playing by playing E9 rather than E one gets the two blues notes that are missing from the B7 chord(usually played melodically).
That is, if you play the E9 from the minor mode(add the min9 rather than the maj9) over a B7 chord you'll get the tonality of a B13b5#9 chord(it won't have the maj9th in it, the C#, but if you followed we replaced that with the aug9th).
All you really have to think about is simply to continue the harmony from the previous chord over into that of the I chord and you'll get a similar effect. Flatten the 9th of that IV chord though which will give you the b5th of the I chord which will make it sound more bluesy.
Now, if you get that, that is, we can use the E(b9) chord over the I chord then it becomes much easier to play those sounds. Now, We can leave any chord tone out that we wish to make it easier to play. If you are only playing 4 notes in the chord then you'll have to leave out one. In this case he is simply playing different 4 note voicings of the 5 note chord all with a B in the soprano which helps tie them all to a B tonality(so it doesn't sound too jazzy/polytonal probably).
You'll never find a B13b5#9 fully voiced because it requires too many notes. It is simply the mashup of two chords played simultaneously(a polychord) that can either be intentional or not.
For example, playing the V chord over the I chord in blues gives
B D# F# A + F# A# C# E
This gives something that is not used in the blues idiom and has many min2nd dissonances
But the biii chord over the I chord gives
B D# F# A + D F A
which contains exactly the blues notes(min3rd, b5, and b7) and gives us a B7#9b5 chord.
It is much easier to think of just playing the Dm chord over a B7 chord to get the blues sound than(of course it alone is not enough). Adding the root B to Dm gives B D F A = Bdim. So playing a Bdim chord also gives the blues sound and has the same effect ad the Dm chord but with the added B helps tie it together(makes it sound more "Bish" than "Dish").
So try a Dm chord over the B7 chord in blues then try an E(7 and/or 9). Try other chords. See how they all sound. Note that some will work better than others. Some will sound cool but will not be blues.
The only thing new you should be learning is that you can play some chords over other chords that do not change them but that expresses a certain color that is appropriate.
What is more important than anything I have said is HOW YOU PLAY IT. If you can't play it in the proper blues idom then it doesn't matter what your playing. A great blues player can just about make anything work cause they know when to use it(although they might not "know" what they are using and how to use it).
BB King, for example, likes to throw in the b2nd note in some of his licks. I really like that sound as it gives a more sophisticated feel. The b2nd tends to be a bad note use in general but works well in certain cases in blues(not emphasized but used as a non-harmonic tone to add just the right color to a line). The same holds for the b6th.
