Firstly will your tranfer be considered as contious employment or as a 'new' job. We merged a few years ago and one of the things was that it is classifed as continous which is obviusly beneficial when it comes to redundancy...
Secondly are your new T&C;s better than the old ones? EG hours, holiday.
If you are going to be losing then there should be a benefit made up.
When we merged we kept our hours and holiday but when I went onto reduced hours I had to sign a new contract which meant the workign day was .5 hr longer.
I then had to fight to get my pay reduced by only 5 hours rather than 7.5 - which makes a big difference in a month.
If you have doubts then join a union and get their advice.