Well how the Navy reacts to pirats taking hostages is each GM's decision. Mine would be a nice ultimatum like "You have 20 minutes to release the hostages. Refuse to do it or try to move/fire up your reactors and you'll be fired apon" followed by a nuklear tipped missile shortly after the ultimatum ends.
-------------You might run the risk of being very unpopular among your marines with this kind of hard-line ultimatum.
Yes, I loose between 14 and 26 personal. But pirats quickly learn that taking marines hostage means death. Similar to what ElAl did with armored cockpit doors and a "don't yield" policy. You can blow their planes up but you can't take them.
------------------Although I do see this hardline approach being more realistic with marine (military) hostages. They knew what they signed on for. If however the hostages are some civilians or well-trained Tukerera Merchant crewmen. Well, I think that the Imperial Navy would try to negotiate the release of the hostages in this case.