Rogoschin - Yesterday I've tried to check youtube functioning at work. We have Checkpoint firewall with internal wireless AP. It is configured to serve wifi clients with http/https requests only. So connecting iphone wirelessly to it I can not work with anything (Mail etc.) except http-based apps.
Before try I disabled edge in my iphone with BossPrefs to be sure that nothing can pass over it.
After wifi connection I tried to open Safari to be sure it works. Then I opened youtube and noticed that everything is OK there. I could start any video, all worked as it should. And very fast.
So my sum - it is very likely that youtube uses http/https only. At least in my case.