Case 1, you have a planned route and you deviates from it (because of accident or you didn't follow direction), proggy should tell you how to get back on the route. This is the arrow direction and distance shown in alert icon area of cockpit.
Case 2, you have a planned route but got redirection because of traffic, you should see notification in cockpit. I don't know if you tested this case yet.
Case 3, you don't have planned route, you don't get any notification nor alert for restriction. Like I said, if you see restriction signs (that doesn't rotate nor have distance), it's most likely from turn_restriction.zip
If you're talking about using truck.zip so you get alert icons in cockpit, proggy knows and report the necessary data in variables used in truck.zip (look at the codes for those variables)
The routing engine flagged truck restriction and the mapping engine will populate those variables to be used in truck.zip This is the reason why I wasn't sure if it was working or not (because I can't test it when driving). Those variables will only get flagged if the conditions are correct.