AFAIK - no.
You should complete quest on any your 50 toon (and get free HK51 for this one character) and it unlocks possibility to buy HK51 companion for any other your legacy character for 1 mio. But there are two seperate types of HK51 companion - for Republic and for Empire. If you buy Empire HK51 for Republic char - you can't use it.
Very interesting sir. Thank you.
I have seen the Republic/ Imperial unlock on both factions toons, would be a major ****** if you spent a million creds to unlock the wrong one. Can anyone confirm this to be correct?