Not dashcams, you can plug IP cameras into a laptop if it have a network plug, but i think IP cameras are not the best of vehicle cameras. but there are CCTV software out there to let a computer act as a Network Video Recorder
you can run several ip cameras into a switch and then that into the single network plug in a laptop, but you will need a okay laptop i assume to handle all this, some old cheap dualcore laptop i dont think will cut it.
The laptop fan will probably throttle up as it need to handle a lot en encoding, and those can be loud
I use a program called smart PSS on my laptop to access my NVR and view / control via my computer, it should also handle individual cameras, mine just feed into my NVR box that i then access to view the cameras.
But thats just one pice of software there are others out there.
You may also be able to do something with USB web cams, but again they are not really geared for dashcam use so results might be less than optimal, unsure as to software here but i figure there must be something out there.
I think you will be better off just using 3 dashcams, the cheap B1W do a okay job and seem stable, so you could have one aimed out front - one aimed at you - and one aimed at your mirror three to get a feel for what go on out back, though the latter might not be optimal but worth a try.
you can always get 1 camera at the time and trial it in different locations, the B1W are something like 50 bucks on Amazon if i am not mistaking.
I got myself covered by a B1W attached to the mirror stalk, nobody will be able to claim i was doing something i was not.