NPAS takes the principle of mutual aid and nearest suitable aircraft attends the next job, 20 minutes to 98% of the population and all that. The problem with Scotland is that it's just the one aircraft for a huge area and it couldn't become part of NPAS without really skewing the criteria. The nearest back up would be Newcastle and they're already very busy.
So, no, a tie in with Scotland wouldn't offer NPAS anything in return.