It is possible to shoot rifle into German main (click for bigger screenshot). Or if you're really evil, park M36 here.
Unless you changed ABC borders in 2.46 it is also possible to shoot rifle into US main (click for bigger screenshot). The image is from 2.45 but I forgot to report this before the update, and no, the warning did not trigger where I was even though on map it's clearly deep into ABC. Again, parking Kingtiger here will guarantee !!FUN!! for the other team.
NOTE: I did retreat after taking said screenshots in order to not attack mainbase, the kills were just "proof of concept".