Samba 3.0's net command internally knows how to lookup a PDC, but will not fall
back to looking up BDCs for certain operations.
For example, user listing, but not changes, will not require a PDC.
More importantly however, a 'net rpc join' may succeed against any Win2k server,
even if it is not a PDC emulator. We should join an available BDC, rather than
'net rpc join' doesn not have the knowledge whether it is talking to a
AD domain or an NT4 domain. That is implicit in the 'rpc' command portion.
And it also does not know if all the BDC's in a mixed mode domain are
WIN2k or later.
If you want to open a bug for user listings being able to talk
to BDC's that would be fine, but the join procedure will stay as it is for now.