This is the same system GAdv has, however they are 2xxx and 3xxx.That is certainly very likely. The park does some work every year upgrading portions of their infrastructure.
My understanding of the phone lines is that if they are the 3xxx are the lines that are the newer VOIP/fiber lines. Someone else might find this interesting but the real difference between the two is that 3xxx numbers in park can all receive calls from an external call. While 4xxx numbers can only be reached through an in park phone call/being transferred from a different number.