We currently have an Asterisk iPBX connected to our Executone. If you can find a way to route the call from your ACD queue out the T1 channel to the Asterisk then you can do whatever you want at that point. If you have an Asterisk server at each of the locations.

How many phone calls do you expect concurrently in the remote offices? I ask because with only a DSL line you may run into bandwidth issues.