Rules 8.05.2 - 8.05.3 describe the possibility of ramming during an overrun. Is this only an option for the attacker (i.e., moving side), or can the defender's eligible units also ram once at the end of their first fire round?
In an overrun, there is no "moving side." Overruns are resolved outside the movement phase. Each side (attacking and defending) both get to ram.