Quote Originally Posted by [URL="http://www.d20pfsrd.com/gamemastering/other-rules/siege-engines"
Siege Engines[/URL]]Proficiency: Siege engines are exotic weapons. A creature with the Siege Engineer feat is proficient with all siege engines, including siege firearms. A creature that is proficient in firearms is also proficient in siege firearms, but not other siege engines.
EWP (Firearms) gets you all firearms, which includes "siege firearms."