E&M is a signaling type listed under T1 CAS. Anything that can run T1 CAS MGCP should be
able to use hookflash. If it is an H323 gateway it will use hookflash relay. So
everything in that list that is MGCP and T1 CAS supports hookflash. The only exception
would be the Catalyst 4000 and 6000. It must use E&M.
For hookflash to work in the IOS, h450 call transfer script:
app-h450-transfer.18.104.22.168.zip is needed and the script can be downloaded
Cisco CallManager 4.2.1 and upper supports hookflash transfer on the T1 CAS ports of all Media Gateway Control Protocol (MGCP) gateways (both IOS and non-IOS gateways).
The only exception would be the Catalyst 4000 and 6000. It must use E&M.