Unless certain settings on the PC now residing in a domain have occurred, you should still be able to access it. These would be such settings that would place it outside of the network as well as the workgroup and mostly have to do with its IP address. It could also be firewalled which could be a problem. If they are still on the same network as far as address "family" access is possible but might require a separate login.
I have a small home network that I connect computers through my wireless LAN for sharing files, printers etc. I recently had to change one of my computers from a workgroup login to a domain login for work. For several reasons too long to go into here, I am not able to log into a workgroup at home and the domain at work, so I am stuck with the domain all the time.
How do I find the printers and shared drives from now that I am now longer in the workgroup?