TUPE protects their terms and conditions. They also cannot be dismissed simply because of the takeover. However, if, once the newco is up and running, there are say, 2 people for one job, then the acquired people are in exactly the same position as the employees of the Co doing the acquiring.
Some sort of "fair" competition for the job/"vacancy" is required.
I think this is a reasonably good guide.
Basic Guide to TUPE