Apparently the players are free game.
According to the article, something called the Vancouver Rapids have already laid claim to Bocanegra, but he will certainly go through allocation where the Vancouver Whitecaps have first refusal if he comes to the MLS. So the Vancouver Rapids, who are having a tough enough time already--not being an actual thing--are out of luck.
Speculative sure, but Bocanegra, Young Pyo and DeMerrit would be one hell of three-fourths of a defense.
I'm not knowledgeable wrt the Scottish league, are there any other MLS targets no longer on that roster?