OK I think most of the answers are quite reasonable. A friend of mine just sent me some pics of A320 CDU and it indeed has live RAIM. I wasn't aware of that as on B737 there is no way to see anything more than ANP. I was trying to google what kind of GPS receiver do 737NGs have but I failed. Maybe there is an algorithm equivalent to RAIM inside but I can't find any info on it.
Another thing is that I really don't understand how could SBAS help doing RNP LNAV or LNAV/VNAV approach? Or why would baro aiding allow for one satellite less in case of LNAV/VNAV? For LNAV, baro aid is obsolete. For LNAV/VNAV baro aid is a must and if it allowed for a satellite number reduction it would mean that reduced number of satellites is in fact a standard number... And for LPV? This is the only, fully RNP GNSS approach and baro aiding here is useless.
I think some of you guys confuse ABAS, SBAS and even GBAS. I've read through dozens of documents on PBN and interchangeable use of augmentation types is nowhere to be found. You can't just use GBAS or SBAS to compensate for lack of satellites in order to perform LNAV/VNAV. Am I crazy or am I missing something important here?