2 ATAs + 1 VoIP Account = Same Caller ID / ANI for Outgoing Calls

[Amiga]

I'm trying to figure out the easiest and cheapest means to get two ATAs, at different locations, to use the same VoIP account for outgoing calls. I have hardware devices, at two different sites, that need their modems to dial out and the server on the other end needs to see the same Caller ID / ANI information, as if both pieces of hardware were dialing from the same location. Maybe one adapter can be configured to receive incoming calls, but outgoing calls on both adapters should reflect the same Caller ID.