Hm if NATS don't get the contract, how will the new incumbents be trained?
In the same way that has been done when NATS or any other provider) have lost a contract anywhere else.
Given the manner in which NATS have been treating new recruits over the last few years, I doubt they'd have the intelligence or the resources to persuade every existing ATCO at Luton to stay with NATS.
What would ensure NATS survival at Luton is the provision of Approach Radar Services. Is the airfield contract separate from the remote provision of radar from Swanwick?
If not then NATS have the upper hand as the new provider would have to directly employ radar rated atcos, engineers and probably pay for the oversight and commissioning of radar facilities at the airport. That would require an extremely lengthy contract to get a financially worthwhile return.