Borg have never been shown to telepathically control someone not already in their collective, long range, Professor Charles Xavier style, like Jack did with Mura this week. Before I could buy the Borg thing becaue Jack touched Sidney La Forge, and maybe he "assimilated" her or something to mentally control her fight with the changelings. Jack never touched Mura. He controlled him purely telepathically, something a Borg has never been shown to do in all their many, many appearances in Trek. If it is the Borg, then they're changing the Borg to fit their plot.