Arriva have publicly (on social media) stated that whilst the live app is a useful tool, it isn't the be all and end all.

The GPS data from the bus for example, has co-ordinates that are sent around every 20 seconds to the server, which then matches the bus to the right journey and plots it on the map for the end user. Its not a direct data connection between bus and your app.

However, this can be fooled if the driver incorrectly selects the wrong trip on the wayfarer - it will show the bus as silly late when it is actually on time, as the server thinks it is operating trip 14 of the day, when it is actually operating trip 15.

It can also be incorrect if the trip assignment at the server end is also incorrect - either with an out of date schedule on the server against a bus running to a revised schedule. This is more likely to happen when recent changes have occurred to the timetable however.