The Plant Daleks were an early attmept at an automated expansion system for the CoPS. After the annihilation of the CoPS, they took a VMT (see Vortex Manipulation Device) and modified it to send you to a random point in time, rather than a random dimension. Doing so, they went back in time to destroy what would eventually be their creators for no real reason. They're for some reason leashed to what was official CoPS territory and seek to have absolute control of the territory of which their now dead creators had taken prior to their destruction. The Plant Daleks are currently fighting a war against the Orange Bots because they're the only thing stopping them from total control of their systems.