That's an interesting question.
Credit Unions in NI are controlled by these people: -
Registry of Credit Unions, 8 Laganbank Road, Belfast.
This is the place where the web links to them (part of the Dept Trade Industry in NI)
http://www.detini.gov.uk
The regulation is different between north and south, but clearly if the scheme is applicable, it is going to be the UK Government's �50k scheme that works in NI.
I searched their website but could get the answer for you - maybe someone else can.