In the event a civil or public servant retires and goes on pension and subsequently takes a position with a Government Department or organisation covered by a Civil Service Pension Scheme, s/he may not earn more by way of their re-employed salary and pension than s/he was earning prior to their retirement. When the salary and pension exceed the salary prior to retirement the excess is deducted from the pension. This is pension abatement.
In relation to members of the Defence forces as referred to in the parliamentary question it is not possible to give a definitive answer without having full details of the matter. The individuals concerned should engage with their current employer (in this case the institutes of technology) in order to establish if the pension abatement principle will apply in the event they receive a promotion. Their current employer will in turn have to engage with the Department/body responsible for their pension scheme.