PIA own existence is at stake, hence keeping the ATR 42 May be temporary as well as the short haul prop flights are generally operated at a loss that is covered via Jet routes profits. In this case however even the PIA jets are internationally grounded. So whichever way you look at it, News is not good for PIA, ATR and PN as well.
No, that is not how this works and is a very simplified understanding of things.
Even of PIA were to cease ATR operations overnight, it would not be detrimental to PN, all it would mean is PN needing to set up engineering, repair and training facilities for ATR. Italian and Turkish Navies have already done this. PN has massive experience with prop planes. PIA facilties are a bonus that makes it cheaper that is all. As mentioned, ATR is one of the most popular commuter planes on earth,
You do not know what you are talking about