IVR’s (if it is IVR, not VTO) are usually physically connected to the PBX by RJ45 cabling, or similar. If you only want to have 1 IVR on 2 sites, you may need to speak with the switch provider to see what is possible.
We have a centralised model for Config Layer etc, but do have multiple sites with IVRs located at each site connecting to the local PABX. In Config Manager we have setup an IVRServer and a TServer IVR for each remote IVR to make management simplier and to enable work to be carried out on systems without impacting others… Its basically a one oone relationship all the way, until they reach URS.