They do go from the 1900 t0 the jets but until then it is a very different deal. Salaries for a start, possibility to bid for airplanes etc...
Also when they do transfer from a Captain position on the 1900, it is as an FO on the jets. For them to become Captain, they will be required to undergo the normal upgrade path within NJE (Seniority, aptitude, ground scool, upgrade sim and line training).
Captains to be on the 1900 are normally type rated with experience on type. FOs,... It varies but people joining will have turboprop time (406, 200, ...)
That's the deal. I see the 1900 as an opportunity for people to join NJE without the usual experience required to go onto the jets. It also could be considered as a part time fleet since one the aircraft is on maintenance, it is holiday for everybody
on the fleet.
+s and -s.... Weigh it and make up your mind on the interview day.