I happened to notice a very slight delay between the radio commentary and the "live" telecast of the ongoing cricket series between India and England. The delay is to the extent of upto 3 seconds. If you have a radio commentary going simultaneously along with the TV telecast, you will notice that the radio commentator has already finished the description of the ball by the time it is telecast by TV channels.
It is really funny when you know the fate of the ball before you see it on the TV. The last time I experienced that it was Sehwag and Gambhir going great guns against the poor Englishmen and it was full of excitement to hear that the ball has gone to the boundary and then see the "live" footage on the TV. But I guess it would be very different when you know that some batsman has got out or a catch has been dropped by our great fielders.
Check out that if you still carry a radio. In Chennai, the cricket commentary comes even in FM radio station 102.3.