How is workgroup in fastpath considered?

Does the workgroup in fastpath considered has a XMPP account(user account) or considered as a MUC room and is there a way to route messages from some commercial and non-commercial IM’s to fastpath.

For example, can a yahoo user use his yahoo IM to add a particular workgroup in his list and start chatting with that workgroup?

They are considered private MUC rooms. If you go to your groups tab you will see the Fastpath workgroups listed there. Access is restricted to the webchat client and those members of the workgroup.