My mods are working but some reason I no longer get the notification on main menu. (I used to, but no longer).
But I have Overwatch and Errortrap and if they are working properly, you should get a note when you load a game and/or every sim day about "x amount of cars deleted". I get that car cleanup pop up every time I load the game, and occasionally I get other types of notifications (like stuck sims reset etc). If you never get any messages, I don't think they are installed correctly.
Error trap only shows any notifications if there has been an error, so it's just good if it doesn't, I guess. I rarely get anything.