The selection is only a small part of the story, if selected you are then on probation until training is finished. Passing training seems to be around 50/50. The housing department were told last year that 140 were coming and to expect around 70 to stay.
It is not designed as a commuting contract, they provide housing according to family size and subsidise schooling. You can get a block of 5 days a month to go home though.