Legalise
I have no idea about DNATA, although my personal view is that I would be surprised is a deal has been put together so quickly. but I can say with some certainty that your other comments have no semblance of truth to them. When a company is bought the entire company is bought and that includes all the staff working for the company at the time and all the contracts they have. The new owners can then do what they want (within the law) as they own the company.
Regarding your earlier comments about how does it work.
Purchaser “A” buys Swissport including all the staff and all the contracts and they rebrand it as company “A”
Swissport acquire Servisair at BHX including all the staff and all the contracts and rebrand it as Swissport.
If you are handled by company Swissport you will be handled by company "A" and if you are handled by Servisair you will be handled by Swissport.
I am sure there must be some small print in any deal about how long it is before Swissport can approach any of their former customers who are now with company A as they will obviously have a lot of proprietary information about these contracts.