Maxed-out... Your source is not correct - Aurigny and Blue Island must advertise locally to see if there are any local pilots. If not then the company applies to housing and historically an FO will get a 5 year housing licence.
With regard to a local getting his/her name on file - that may be true, but without a rating they won't get any further than that 'cos neither company pay for ATR ratings.
So, to summarise, anyone wanting a job needs a rating, local or not.
It is NOT a case of who they prefer - if there is a suitable local with a rating, housing will not issue a licence for a non-local.