Allyn Gibson wrote:
I'm not sure how the Borg nanotubules would reach a Dalek mutant inside its travel machine.
The mistaken assumption there is that Borg nanoprobes only affect organic matter. They affect technology as well. (E.g. in VGR: "Drone," some of Seven's nanoprobes contaminated the Doctor's mobile emitter, which in turn extended tubules and assimilated the computer console on which it rested.) The travel machine could be assimilated first, and then turn on the mutant inside.