Though not widely talked about, I desired to access files on the Home$ share of a Samba server from my Linux workstation. I had never come up with the syntax to do so.
Using mount.cifs to do the mount, it turned out to be simply //server/userid and no trailing $ or anything special.
Obviously I made sure that userid was the same user that was authenticating to the PDC in the first place. I did not try accessing bar's Home$ share using the ID foo, for example.