I would say that E minor seems to be the clear prevailing tonality in this example. You have B chords going to Em chords, and that's quite common in minor (theorists call it harmonic minor when they raise the seventh note to the leading tone). Every note in the chords you wrote actually fits into E harmonic minor. Even the C minor chords have that E♭ = D♯ note (at least for a listener), but that's actually not the best explanation for the C minor chords:
The C minor chords do complicate things a bit, but the Cm (2nd chord) can be explained as a chromatic mediant - the root jumping up or down by a third to form a chord outside of the key for effect. That's not a particularly functional concept, but that doesn't mean that it's wrong either - just that it distances itself from the E minor key center a tad bit, which is perfectly fine. The Cm6 chord (last chord) could be explained as the same thing, but it's worth considering that the Cm6 chord can be interpreted as the V7♭9♭13 (or V+7♭9) chord, an altered dominant chord whose root is implied to be B, leading nicely back to the E minor chords at the start of the piece. This is especially likely due to the chord preceding it also being a B altered dominant chord (B+ means B augmented), making for a full final measure of the B dominant sound (even if I misinterperted the length of the measures, the explanation holds true).
"Can I really consider this an Em progression with a resolution?"
If you buy into the altered dominant idea, then your progression ends on the V and loops back to the i.
It doesn't get much more resolved than that, my friend.