if the business is ceasing due to financial difficulties and staff are being made redundant then you may have an entitlement to redundancy and to take up the new job. a lot will depend on your employers role within the new company/business i.e. is it him setting up a new business or is he getting a job in a new business and there is an opportunity for you.
I expect you should either transfer your 15 years or get redundancy - one or the other.
also, if the employer is unable to pay the redundancy for bond fide reasons (no funds etc) then the state may pick up the tab for the redundancy amounts.
it is an important time and a very important matter so make sure you get the correct legal, tax and dept of enterprise advice.