replicating directories

Setup a trust between the two domains. Open user manager for domains, policies, trust relationships

The domains already are connected by a trust and we can access each location. What we are trying to do is reduce/regulate the traffic over the T1 and speed up access to these files. Each office only needs read access to the other drive, so I was thinking of automating the process of copying the contents of drive A in server A into a read only directory on server B abd the contents of drive B in server B into a read only directory on server A. Advice on how to do this?

You didn't say how often the data needs to be updated from domainA to domainB and visa versa. That makes a difference in the apporach.
If it needs to be real-time, then I suggest that you should just map domainB to the files on domainA, with the Security permissions set to Read Only for the domainB users. It will not remove your banwidth concerns, but if you think about it, even if had a replication program going 24/7, the replicated files are gonna take up bandwidth. So either way, you are gonna lose some room in the T1.
Now, if it is not important for the files to be visible in real-time, then I would set up an XCOPY job to run. XCOPY all of the files from domianA to a server in domainB, and set the permissions on the domainB folder structure to be Read Only for the domainB users.
Set up a BAT file that maps a drive to the shared folder in domainB that you want to copy the files to. Do the XCOPY. Like this:

Net use F: \\DOMAINB\SERVERNAME\SHAREDFOLDERNAME
XCOPY /E /C /Q /H /R /K /O /Y c:\files\*.* f:\

A few things to keep in mind doing this. 1) make sure that when you set up the Scheduled Job to run the BAT file, that you define it to run under a domain account that has sufficient rights in your domain AND in domainB. If not, the drive mapping will fail (which will make the xcopy fail)
2) the /O switch for XCOPY says to copy over the ACL to the destination. That might cause you a problem if domainA\User1 sets the permissions on a file too tight so his friend indomainB cannot read the file. If you do not include the /O switch, then the files will inherit the folder permissions of the destination folder.

Hope this helps.

I'm trying the 2nd recommendation mentioned below. The issue we may run up against is that it could take several hours to do this. While we only need this data replicated 1x a month, looking at 10-60 GB of data is going to be a considerable amountof time across the t1. Is there a way to do replication in 2000 so that only the changed files go across? I found a switch for Xcopy that may do this, but just in case it doesn't ...