[Freeswitch-users] Migration to FS

Is there a document or recommended strategy on how to migrate from an existing PBX system to FS?  There are 2 T1-PRI lines used 24/7 (call center) which can't be down for development or testing.  The existing system is InterTel. I have a Sangoma A104D available with a tap ready to be installed.  I'm thinking (hoping?)  that I can start by using it to monitor and/or record calls without interfering with the InterTel.