Question : T-1 muxing converted into a signal that can be terminated at a cable modem

A client has a WAN(campground) of coax termination points that can be connected to the local CMTS(which is on site and owned by them).  What they want to do is mux a couple T-1's with internet access and send that signal out over the coax to terminate at the existing cable modems.  Does anyone know what this kind of converted would be called, and if it would work if there was also cable tv signal going over the coax (the T-1 data network and coax cable network would have to be merged onto the coax).

Answer : T-1 muxing converted into a signal that can be terminated at a cable modem

Your most likely looking at a very special piece of equipment that would be like a router that breaks the t1's to coax. Your big problem is going to be the TV side. At this point for you and your clients sanity i would be looking at a cost factor and also exploring different options.