I think it is very important when the Government spends our money on infrastructure that the overall benefit in efficiency for society is higher than £1 for every £1 spent. Generally good infrastructure project return about £2.50 in cost reductions / efficiency improvements for every £1 spent.
Without knowing the investment v return ratio that the Government has calculated to the cost of investment on this, it is impossible to tell whether this is a good or bad investment of taxpayers money, although I suspect the latter and the money would be better spent elsewhere for a better return for society.
Personally, I like the way the Americans talk about "our tax dollars" as the only money Governments have is what the take off us through a process of legalized robbery. It would help all people to remember this if we talked about the spending of "our tax pounds" in the UK.
As for austerity the only cuts being made are to pay the ever increasing amounts of interest on our national debt. Without high inflation by 2015 we will be beginning to reach the point of no return on this. Yet they continue to borrow and spend money like water as if there is no tomorrow. Still I guess if you only expect to be in power until 2015 you don't care.