PRI Call Recording using Asterisk

I need to set up a call recording server on a site with an existing PBX. Unfortunately I can’t just replace the whole PBX.

Is it possible to connect a 2 port PRI card to the PRI connection in a “passive” mode using a y-cable (ie so that it does not interfere with the existing PBX) and let Asterisk listen to the line? I was thinking I could then use the Asterisk Monitor() command to record all calls.

Has anyone tried this or anything like it?