I share your scepticism to a degree, on the other hand:
1) the Dome was actually built to time and budget, just the exhibition inside wasn’t any good
2) construction’s going to be in its worst recession for decades over the next 4 years, so contractors and staff bidding up costs aren’t going to be as much of a problem as expected when the bid was made

Okay the construction aspect of the MD may have gone to plan, but the project itself – the dome as a going concern and the £1m-per-month maintenance costs over the 6-years it sat empty, suggests we have a lot to worry about.

construction’s going to be in its worst recession for decades over the next 4 years

Excellent point.

However, regardless of the supply and demand of construction workers (also remember major projects are probably already approved), the urgency of completion may give power to the construction companies, who in a difficult market, may see the Olympic park as a cash cow.

I hope you’re right, John.

The problem is that if a project has to be completed by a certain time, you can’t maintain cost control.

It’s important to remember that the budget was set long before Boris was elected and contains over a billion pounds worth of contingency.

Boris isn’t actually announcing anything new here.