Can a fax call be redirected?

I understand that it’s best to use pstn or pri lines but in this case, I need to keep trunks virtual, meaning, I can’t have hardware in the boxes. That will change down the road but up front at least, I need to take advantage of wholesale level pricing which I can’t get with physical pri’s.

So, on my network, I have a pri to sip gateway. When calls come in, they come into the gateway, then sip is sent to the pbx. The user only has one DID on pbx1.

Is is possible to forward only fax calls to a second pbx? I’m not sure how the system would be able to recognize that it is a fax call and send it, without answering? Probably can’t be done.

Something like;

pbx1: Has a users DID on a SIP extension
pbx2: Has a second extension which is IAX for same user.

When fax call comes in to a certain SIP DID on pbx1, have that call recognized as a fax call through nvfax or something else, redirected to the other extension on the second system, where all of those extensions are IAX and accept fax.

This would also help in that faxing over the system would not bog down the voip calls/server.