I would guess if LLAL/ Luton Council defaulted on the loans they would have to sell assets which would mean selling the airport. Also estimated costs will no doubt rise as when first announced the existing redevelopment work was costed at £100m. The latest figure I have seen is now £160m with a nearly 2 year overrun on the terminal project.
There is no doubt that the council is gambling on getting the numbers but if it all goes wrong those making the decisions today will be long gone with the new councilors saying it was nothing to do with them.