Any changes to the %systemroot%\SYSVOL folder on any DC are replicated to the other DCs in the domain. Replication is RPC based.
You can use NETLOGON and SYSVOL to distinguish between DC and member server. If both the NETLOGON and SYSVOL shares exist on a W2K server, it is a DC. When dcpromo demotes a DC to a member server, the NETLOGON share is removed. Thus the presence of only SYSVOL signals a member server.
A neat method to check which servers are receiving replication (example is W2K but technique is general): create a file to be replicated which has the same name as the name of the domain controller. Lets say the DC is named w2ksrv1, in that case create a file
\\Winnt\Sysvol\Sysvol\yourdomain\w2ksrv1 Check which domain controllers in yourdomain receive the new file.