The current laws around mobile phone use in the car are rather restricted, in that it is only forbidden to call or text while driving. Given this restriction was introduced about 20 years ago now it made sense, as all phones could do was call, text, or play Snake.
Today though you can do everything on your phone, from buying music, to composing letters for your job, and this is a loophole that motorists have been using for years to avoid punishment. Instances of people pointing out that they were filming with their phone, rather than using it to text or call, have been common, but it is all distracting motorists from their driving, and causing danger to all others around them. Some apps have been offen blamed for dangerous driving, such as Snapchat and its notorious "Speed filter"
While they are still looking into the specifics at the moment, it seems logical that they will just blanket ban all phone use (save for hands free connectivity), and make it clear that it is not acceptable to use your phone while driving. The exception for contacting the emergency services is unlikely to change however.