I have an Epiphone 61 SG/Les Paul Custom reissue. The wiring is as follows:
3 individual volumes/ master tone.
Treble - bridge & middle
Middle - all 3
Rhythm - neck & middle.
If I dial out the middle pickup the 3 way works just like a standard 2 pick up model. If you have all 3 on you can get tones you just can't get on any other axe.