Yes they can. Just be sure the alliance member that wants gets the last attack in. If not then whoever took it can abandon it for the player and or if you guys don't have enough room for that sub it will become an NPC sub.
When fighting a boss try to have 1.5 to 2 times more power than the boss. Say if a boss has 1.8M power then bring like 2.5M power or more to kill it.
Centurion