I don't see any issues having multiple devices connected to the same set of DNI/wireless display devices. If you try to have 15 AR windows open at the same time, however, you'll run into the -2 dice pool penalty to Perception tests for being distracted by AR.
But really, the scenario described by the OP to my mind is like having multiple devices hooked into the same display; picture-in-picture/picture-by-picture if you will. I don't see a reason why a user couldn't have notifications from multiple devices pop into view when relevant.
It'd be like having a message notification, a call-waiting notification, AR directions, and your smartlink system notifications pop up in serial instead of tandem (i.e. all over your range of view). For having both (or multiple) devices transmitting in unison I'd impose the -2 dice pool modifier for distraction, but if they were both (all) configured to just give "balloon" type notifications in the side-view similar to some HUD tech available today I don't see a problem allowing it as is.