pretty easy to catch on a rail you're running parallel with even with 2" tires when wet. fatter tires do make them easier to deal with, of course.
when going across them or expansion gaps mentioned earlier in thread, cross at greatest angle you can. pop wheelie the front wheel over, then unweight the back wheel when it crosses. If you have to deal with a lot of these, consider backpack or messenger bag instead of rear panniers, as they can make efforts at unweighting rear of bike less effective.