Lately they've used split-screen to show simultaneous actions by different people. It works rather well, because while the videos show different actions, they both fit into the same coordinated plan.
For a few seconds at a time, during transitions between scenes or in the lead up to advert breaks. Synchronicity of relevant actions is minimum - ie a car driving, while someone sits in a room. the other two may be 2 sides of the same phone call.
There's not really ever 2 concurrent plots happening simultaneously.
