Should be yes.
As my mac is 2006-era it has a very old USB chipset, and this has caused unexpected problems in the past (e.g. with USB audio). I don't know if this could affect booting from a USB drive.
Anyway I've posted a question on the Apple forums:
https://discussions.apple.com/message/17288539
And I've also raised a support case with LaCie.
Will see what happens.