I thought it was in effect from the start of the transfer window until 2 weeks before it closed.The final 2 weeks of July are the only time the clause comes in to effect. So in essence a club can't bid until those final two weeks anyway.
Every club knows about the clause so they wont be bothering with anything until it comes in to effect. Which ever Manchester club fails to get Maguire will most likely bid for him as a back up in my opinion.
I hope I am wrong, I hope he stays but the writing has been on the wall now for a while.