My guess is that it will relate to which roads it wants to route over, so it may or may not work depending on starting point. If you were to get somewhere that overlaps the suggested route from Allentown, PA to Springfield, MA, can you route it? That is if you're not too far away to do so, of course. I think it will fail if you are at a point that would use the same route that I'm trying to use. I'm just not sure. I really need to route there in a couple of weeks and this is going to be a problem. I would rather use Waze than Google on the trip.
Just to get a more specific routing than an entire state, you can use Greensboro, NC to Springfield, MA. I prefer not posting exact addresses or cities where I am at online, but routing between those two locations will use the same route I'd be using. That may offer a better testing experience than using the enter state as the starting point. I also tried other places in MA that route through CT, such as Boston, Worcester, and Salem. They all fail to find a route.
I'm not sure if this is a routing engine problem or a problem with the roads, but I can route all over as long as I avoid SW Connecticut. For example, I can route to northern Michigan, which is a longer route. I can also route to NW Massachusetts, which bypasses CT. That said, it does appear that there is still a limit on how far you can route. I can route somewhat over 1000 miles (Oklahoma City, OK or Houston, TX), but I can't route all the way to CA or even to CO.
Michigan - Northern LP.
Waze running on Samsung Galaxy S3.