Do you know for definite that they will be automatically "TUPE'd" accross to Eastern?
Have a look at:
TUPE - a guide to the regulations
Quote below from above website:
Transfers not covered by the Regulations
The Regulations do not apply to the following:
transfers by share take-over because, when a company’s shares are sold to new shareholders, there is no transfer of the business - the same company continues to be the employer;
transfers of assets only (for example, the sale of equipment alone would not be covered, but the sale of a going concern including equipment would be covered);
transfers of a contract to provide goods or services where this does not involve the transfer of a business or part of a business;
transfers of undertakings situated outside the United Kingdom.
Looks like the third one down applies to Eastern's aquisition of the IAC contract.