They might fit as these racks are actually run pretty wide inside. Height might be a bigger issue. At worst you might have to build a small spacer piece on the bottom rack eyelet to raise it up an inch or so.

I personally used a 2.4" x 29" mountain bike tire on a 23 mm rim on a Tubus Cargo with tons of room to spare.

Tubus now makes a fat bike rack that should most definitely fit your bike. 26" fat bike tires are the same diameter as 29"+ tires. The rack is designed for wider spaced hubs however.