If we have a power blip on the SPB side and only have a SPS on SPA will SPB immediately go down? Or does the SPS provide power to both SPA and SPB thru SPA?
The power supplies for each SP are for its own SP. They are not redundant with the peer SP's unit.
The EMC Unified Storage System Fundamentals for Performance and Availability in the VNX power supply failure behavior section has more details. VNX Fundies is available on Powerlink.