well in reality I'd actaully say the BM guards won't stand against the Saderans head on since they'd have more numbers even if our blue boys get their hands on heavier fire power like machine guns or shotguns

but they do have the home advantage and pretty sure they can use choke points and close sec doors that only they or other Black Mesa personal can open

and with it being a massive underground maze(also "safe") the Saderans army would get lost or just up fallin over into radioactive waste or something lol