I believe RAIM is only needed for GPS only navigation. On the boeing (well, 737) there is no RAIM indication at all, we simply do not need it. We do have ANP indication though (on the LEGS page in the CDU, on the ND and as performance navigation scales on the PFD), and that seems to be sufficient even for GLS precision approaches, not to mention all the usual RNP 0.1 stuff we are approved for. Check CAP 773 2.2 b). It might well be true that the GPS receivers use RAIM internally to check if their output to the FMC is still valid. Funny enough i have never seen a dual GPS failure so far, however occasionally i do get a message GPS 1/2 INVALID which indicates that one GPS is not used anymore. The remaining GPS is enough for RNP 0.1 operation, for PRNAV no GPS at all is required.
As GA navigation relies usually solely on GPS for that kind of stuff RAIM is necessary, but that is not a general rule for all kinds of aviation.