I wouldn't necessarily say any 2.2 tire would fit until tested. For reference I'm running the 35mm wide , which is 30 on the inside. Have a 2.1 Thunder Burt mounted on there, but is extremely difficult to seat as the tire doesn't want to spread out that much without some help. So on a 35mm wide opening some 2.2 tires may not open up enough to seat properly, which may leave them to burping or rolling off the rim in hard use.
Bottom line, if running a 42mm wide rim, you ahould probably run a 2.35 minimum, more likely a 2.5.