Technically yes, but I'm not sure how readily that would occur. Fish from the same genus usually will readily cross breed, while fish from separate genuses will not breed as readily. With mbuna (and really most african cichlids), if you aren't careful they will likely interbreed. The best way to avoid it is to keep good ratios of males to females (1 male to 3-4 females).
I have an mbuna/hap tank and don't get interbreeding. I did choose my species to try and avoid this, but I know plenty of people who have very similar stock lists as me (but not good M:F ratio) and get tons of hybrids.