I thought I would pass along some useful info:
We forgot our NY ezpass on our trip this past weekend. I remembered (that I forgot) while we were in Maryland and we were able to get one at a retail store and call in to activate it.
However I have discovered that the states will give residents discounts. It cost the MD tag user $15 bucks to cross the Verrazano Narrows Bridge, where it charges a NY tagger something like three bucks less depending upon whether it's considered peak hour. (Can be as much as $5 less)
NY is easily the most damaging state as far as tolls go, so if you go there, get one of theirs. The MD one only gave a 10% discount in MD and charged a $1.50 a month fee. The box was $9 + a $25 preload.
So I have cancelled the MD account and added another NY transponder to put in my car. Note that if you get an individual plan for use on the NY Thruway it waves the $10 signup fee and it can be used anywhere. They will mail it to you as well.
If I95 in NC goes toll I may get a local box. Because NC residents should be free and out of staters should get squeezed since they don't pay our road taxes.
Hope that helps.
Dave