I replaced my four rear 295/80R22.5's with 11R22.5 in March, 2011. They are the same diameter and nearly identical revs/mile, so work fine. Cost a bunch less and 11R's are usually readily available wherever you may be.
However, I can't use them on the front because they have less load carrying capacity than a 295/80 LR H and my front axle is heavy (14,600 lb GAWR). I would have to use 12R's there, and that should not be a problem even though they are a bit larger than the 295/80. I have Goodyear G670's in 295/80 LR H on the front now and they are good for another three years, so haven't made any decisions yet.
2004 American Tradition; 2014 Buick LaCRosse
Homebase in the Ocala Nat'l Forest near Ocala, FL