I want to say I've fragged a few tanks with a Yak - T as well in the past, but I don't recall if those were simply bail outs. I believe I saw a couple legitimate pops. Course' you could make the argument that the Yak T is a tank buster...
The Yak 9t is no tankbuster at all.
It may sport the same NS-37 cannon as the Il-2, but apparently it carries different ammunition.
I tested it extensively offline vs the stationary Tiger. The Il-2 had no problem killing it or at least disabling it's turret with 10-40 rounds. Each attack run results in a dead or disabled Tiger.
When testing the same with the Yak-9T (with ammo multiplier set to 10, giving it 320 rounds), I couldn't even scratch the Tiger with a lot more hits. Most notably was the difference in hit sprites: When flying the Il, i would see a lot of hit splashes on top deck armor, whereas with the Yak the rounds would often just ricochet when striking the top armor at the similar angles and distances. Unless striking the tracks, I rarely saw any splashes at all.