Auth Services and Domain Trusts


Looking for some help and advice.

I have a Active Directory that I administer and can install Auth Services into. Within this AD I have some admin users that need access to Redhat machines, all no problem with Auth Services. However, my question is this.

If the AD at the other end of the Trust has users that I need to "Unix Enable", so they can also access the RedHat machines using their AD accounts, is that possible?

Note - the other AD is managed by another company and I have no possibility of getting anything installed or changed other than a trust established.

Can anyone help/suggest if this is possible?