I see no reason why it would not help. In fact, it would help bring to the fore the issue that if we have transparency, then we should have no problem at all with UN mechanisms investigating.
I don't know if it will result in a positive response on the part of government because, after all, UN bodies would look into the larger field of human rights. A study mission can look into Canadian firms, which is probably a reasonable prerogative on the part of Canada, but for the UN, it would look into various aspects, so I'm not at all too sure if the Philippine government will immediately accede to that. I see no reason that would not be of help in the current conditions.