Whoa, a lot of misinformation in this thread.
Long story short, this person is right:
1. Get a BB30 crank
Use no adapter, just BB30 bearings, on the BB30 bike and a Rotor BSA30 bottom bracket on the BSA bike.
2. Get a GXP crank
Use a BB30 to GXP adapter (wheels mfg and others) on the BB30 bike and use a GXP bottom bracket on the BSA bike.
Either should work.
Any model year of SRAM Quarq BB30 will work with a Rotor BSA30/Zipp Vuma BB on a BSA frame. The same goes for S900 and S950 BB30 cranksets.
They do not use Rotor spindles.
They are not transferring the S900/S950/S975 standard to any other cranksets. Any of their other BB30 cranksets will not work on a BSA frame.
Edit: Personally I'd go for Option 1. The less adapters the better, in my opinion. Plus it ends up being lighter if I recall correctly.