Flight International included a civil simulator directory in a recent issue, and from the look of it, whether 330/340 simulators (for example) are common depends on the specific simulator. Most airlines that have both A330s and A340s seem to have joint "A330/A340" simulators (the same exact simulator with software and throttle-quadrant changes, I guess), but occasionally they have additional simulators specific to one type or another. Also, A330/A340 simulators are never shared with any A320 family aircraft, but there is often "sharing" within the latter. It all depends...
As for 757/767 joint simulators, there are some of those as well - Air China, for example, has one. Like Airbus, though, there are also seperate 757 and 767 simulators, so it definitely varies.