It is quite different. Wikiprojects are focused into the producing the rules, layout, etc. of pages on some topics.
The idea of experts communities is to permit communities with larger aera of interest than Wikipedia. Then such communities would have more periferic participation. This mean that they will have stronguer dynamics and recruitement.
The key is to link thoses communities with wikimedia projects contents.
Example : Communities discuss, share news, etc. They also like to have base of contents where they capitalise them knowledge. The wikipedia pages on the community topic could be the knowledge pages of the community. then the community would participate even more to enhance this content.