How much route knowledge a guard gets will depend upon each company’s standard. Therefore it’s variable, therefore, it’s not really that relevant since it works fine for the lowest common denominator. The railway rules even say that it’s for companies to decide what level of route knowledge they believe is adequate for a guard themselves.
Guards need route knowledge for station signals as long as they dispatch trains. The other route knowledge for tunnels and level crossings is about identifying locations and broadly goes back to emergency protection or pulling emergency brake handles. This bit is borderline redundant. Emergency protection rules surely won’t survive another five years in the rule book (at least in the current form), so guards won’t require that route knowledge. In the 1995 accident at Ais Gill, the guard didn’t do protection or follow the rules of course and that was the key cause of the accident, but the GSM radio is now in place everywhere and theoretically provides vastly superior protection arrangements than the guard in the night time with his red lamp.
It would obviously be very useful for passengers if guards had as much route training as possible on their routes for non safety/railway knowledge, such as places of interest, locations of cash machines, transport connections, locations of the stations to towns etc. Unfortunately this would be seen as de-skilling guards by many when in fact it is the reverse.