If I'm not mistaken, Tire Rack tests the wet traction of a tire but not the hydroplane resistance of a tire. I don't see how you really could assign a number to that unless you just drove a car through x inches of water at y MPH and steadily increased the speed until you had loss of control and then repeated the tests over and over while increasing water depth. The results would obviously be much different with, say a 50% worn tire. Also, the marketing hype is that the V shaped tread forces the water out to the front and away from the contact patch.
I will say that of the tires I've had, (Goodyear RSA's, Firestone SZ50, Goodyear GT +4, Goodyear Regatta 2's, Firestone Wilderness HT, Goodyear American Eagles, Goodyear Eagle GA's, Goodyear Eagle HP's, Cooper somethings), my current set of Goodyear Eagle F1's display outstanding hydroplane resistance, much more so than the SZ50's with their directional tread. The F1's seem much better, even with 5/32 remaining than the others (except the SZ50's) when new. I know the tires are apples to oranges in terms of performance levels but I wanted to give a range.