As the Regular Season progresses many Networks may find some of their shows getting killed in their timeslot by a bigger/better show. Naturally one of your options is to move the show to a less competitive timeslot. BEWARE just like in real life, if an audience cannot find a show then they cannot watch it. If you move your show around too much the audience may miss it or get sick of chasing it around week after week. One of the way a show builds up ratings is by word-of-mouth, and if no one knows when the show is going to be on then the ratings will not have a chance to climb.
Ultimately the final decision is up to the Network. A good show that is scheduled in a bad slot will get bad ratings. So the Network has to decide whether the show has reached its ratings limit or if there is something that can be done to up its ratings.
Now onto Cancellation:
1: A show can be cancelled at any time. To Cancel a show all the network has to do is email and tell me what show they are cancelling.
2: If a Network "A" cancels a show then Network "B" should contact the Production Company. If they can work out a deal then they can forward it to me, order a few episodes, and start showing it.
3: Now say some Shows have been cancelled but still had a handful of episodes left. If the other Network wants those episodes then they need to work out a deal with the cancelling Network (Since those episodes are technically still their property). Of course you could always just order some new episodes and not worry about it.