It depends on the crankset - pretty sure all the SRAM 8-bolt cranks that are labelled as BB30 are actually BB386 (so will work with a BSA30 bottom bracket).
From the information collected, I confirm that it is possible to use my Quarq crankset with DZero power meter on frames with a BSA bottom bracket shell (68mm) as it is actually BB386 (the axle is 86mm long)....it should be sufficient to fit the bottom bracket BSA30 with external caps.
At this point the possibility of ordering the Spcycle R088 frame becomes concrete.
I'm still waiting for Spcycle's response to my email....the Chinese New Year should end tomorrow and so perhaps the answers to my questions will finally arrive.