1 - Government 'sells' 49% to the Airline Group, who put in ~£60m of their own money and then borrow ~£650m, saddling that debt onto NATS. (2005, shares were valued around £1.20 I recall?)
Quite normal practice, it's how most takeovers are financed, just look at Manchester United and Liverpool for examples. Normally it evens itself out because when they sell the company the outstanding debt will reduce the value of the company by that amount. The interesting difference in this case is that they only bought half the company but the debt will reduce the value of the whole company so the other shareholders lose out. The staff can't really complain because they got the shares for free in the first place and Gordon doesn't mind because he ran off with the cash from the original sale but as a taxpayer I ought to be a bit peeved.
2 - If the Airline Group then decide to sell out their 49% share, with shares now valued at ~£2.10, and that share of NATS valued at around ~£1.2bn? .... would the Airline Group then be able to just walk away with a cash profit of 90p per share (plus the £45 million 'one-off' bonus they received this year) ? I make that about £350m profit.....
Be careful not to confuse the artificial share price created to allow the employee shares to be bought and sold with the true value of NATS. NATS shares aren't traded on any market so if somebody buys NATS from the Airline Group they will have to agree a price. A lot of very expensive accountants, bankers and lawyers will get to decide what that price is. They will be able to walk away with whatever profit they make after they've paid any taxation due on it. Again this is not unusual many of the organisations sold off by both the Conservative and Labour Governments were sold again within a few years for great profit.
3 -New owners come in and buy it .... can they just borrow the purchase capital and dump the debt on NATS again ?
Probably not. What we found in 2002 was that NATS can't support much more borrowing than it currently has without being financially insecure. It is unlikely that the Regulator would allow the debt to increase by that amount. That also makes an employee buyout rather unlikely. Think of a likely figure for the value of NATS and divide it by the number of staff to work out how much your share would cost. For most people it's probably a little more than they can afford.