For bikes/forks with caliper brakes (sidepull), its the brakes that affect tire clearance, not the fork. The fork is plenty wide enough for any tire, up to 28mm anyway. Its getting them through the brake blocks and under the caliper arms that is the problem. A 28mm tire will work fine with short reach calipers. Except you will have to deflate the tire to get it past the brake blocks, even with the quick release open.
I have a Wound Up on my Seven and as Russell said, I'm limited to the brakes I'm running. I can run 25mm tires with my older Record Deltas, but with my much newer standard Record calipers I can fit a 28 mm tire. If I ride the 28's across any sand, dirt or debris that holds to the tires the brakes clean it off the tire. It's that tight a fit.
Bontrager makes a fork I have in my Lemond. I have it set up with Sachs New Success brakes and 28 mm cyclocross tires. I have set of 28 mm Michelin road slicks (bottom image) that I can run with plenty of room. Most of its life it rolls on 25's.
For bikes/forks with caliper brakes (sidepull), its the brakes that affect tire clearance, not the fork. The fork is plenty wide enough for any tire, up to 28mm anyway.
Except that there are lots of forks where the crown clearance is very tight and people report that a 28 mm tire rubs the underside of the crown. This problem is much more common than the tires being too wide to fit through the brakes without deflating.