idk about all this
For one, it's VSELP, not VSLEP, idk if you're missing the right keys or what. Vector Slope Excitation Linear Prediction.
But secondly, and I was originally wrong here too with the thinking that Motorola will have nothing to do with 3600 baud systems. They still support it and probably sell it too, I mean all of MARCS is pretty recently manufactured and 3600 baud. Also, 3600 type trunking supports analog and digital talkgroups where 9600 does not.
The local airport here, Detroit Metro, recently installed a brand new 3600 analog and digital trunking system for airport ops. The police are digital, the rest of operations, FD, security, etc etc are all analog and probably still on the old MTS2000 radios used back when I worked there and everything was analog 3600 trunking.
VSELP is old, and I know that MARCS is eventually supposed to migrate to 9600 as well, but it will be pretty costly for sure, especially depending on the types of radios used on the system
The article doesn't go into any detail (obviously) about what kind of zone controller they bought in 2005 and what trunking protocols it is supposed to support. They don't make any mention of who said it would be incompatible with anything, but if the upgrade project is going out to bid, it will probably find itself useless with the implementation of a new MA/COM OpenSky thing that other cities and states have foolishly fallen for with their least expensive offering, which would be unfortunate knowing what problems it causes in the long run.