The interesting thing about the BBC article is that it doesn't specify what it means by imminent. It says:
Defence officials say plans for the withdrawal of British forces in Iraq are well advanced.It's clear - from other articles - that the troops are today being taken off combat duties and that it's a question of getting them home, but how long can that take? The point is of course that they surely must be home well before the end of July - three months away - and almost certainly before parliament rises earlier that month. In that case, the government will have to set up the inquiry it has promised.
So what is the cause of the vagueness? Is it operational - or to help the government out of a tricky political issue? The BBC has previously said that the troops will be out by the end of May but that may have been a slip of the keyboard. The Times today says that "all British troops" will have left by the end of June. Apart from that, the media coverage is sticking to the increasingly implausible line that it could take until the end of July.
I suppose we will find out soon enough.