Thank you for replies.
Indeed, it seems it is a case of the EBS following AIB internal banking rules, and not a CB rule ,which was reason given when I queried this with EBS.
This from AIB's tracker retention documentation.......
"You can only avail of Tracker Retention for the amount of time remaining on your existing tracker mortgage loan(s) at the time of application, subject to AIB’s maximum age. i.e: subject to clearance by your 66th birthday or on retirement if earlier; or if you are self employed by your 71st birthday".
It would seem that EBS is no longer a separate , self governing and decision making entity and any interaction with them is in effect an interaction with AIB. Alas, it would appear I have unwittingly, become a customer of AIB.