Wow - this is terrific news. If they can get other types as well, this could end up being one of the biggest advancements in medicine.
As for the Borg, my guess is that this would likely be a "conscience matter". I'm sure they would come up with some twisted logic about how these blood cells were never in a body and thus never part of the "life force" of another being. I think the legal dept would love to make all blood conscience issues because I'm sure they concerned about the liability. I don't see them putting the clamp down on any new techinques and they're probably hoping that science helps them out and eventually figures out a way to eliminate the transfusion of the 4 forbidden forms.
If (when) science figures out a way to mass produce this stuff, it would be the out the WTS is looking for IMO.