likely you have wall studs every 16" and the plaster is ontop of that,doubtful you will be able to route the wires horizontally in the walls,but between the wall studs is a open vertical space , so if you get into one of those open cavitys you can run the wires up into the attic, or down into the basement then run across the room to the other location & do the same.
Fishing wires is time consuming,and almost an art, patience is paramount to a nice job.
If you're not comfortable doing the work yourself, I would try contacting an electrician , alarm company , or even a cableing installer and see if they would assist. A few hours of proffesional labour could go along way to minimizing damage to your plaster.