you should check in the oddball section, but i believe this is a definate no. I don't know what their water preferences are, but spiny eels need sand and places to dig, while malawis prefer rocky tanks. Also i don't think an eel could defend itself against malawis and, being prone to bacterial skin infections, i think keeping them in such an aggressive tank would only lead to problems for the eel (and your wallet).
also, they'd get next to 0 food. I believe the water preferances also disagree, but I'm not entierly sure. I've seen this before and I believe it was cfc who said no.
The problem is the huge difference in feeding requirements, spiney eels need small live and frozen foods like bloodworms and tubifix while mbuna cichlids must not eat these foods ever as it causes bloat which will kill them.