I have no idea where they get their information from - and note that their last update is 30 mins ago, but worth keeping an eye on:

Live: Iran in turmoil

From that link:

”14.39 Footage from Tehran is now emerging showing pro-Musavi demonstrators on the streets - it is not clear whether they are on the way to the main square where the hardliners are showing their support for Ahmadinejad and Ayatollah Ali Khamenei. ‘