This is my view only, but even if trains were running every day, it's still useless to me unless they expand the rail network.
Not a chance in hell I'll leave my car parked at Bellville Station (or anywhere for that matter). Besides that, it's 20 minutes drive away from me... on a Sunday afternoon when there is no traffic.
City of Cape Town is obsessed with "stimulating the use of public transport", which is mostly non existent of you live in the Northern Suburbs.
Even simple things like a team line from the R302 to Bottelary Road with stops in between and and an interchange at Brackenfell Station would be a massive help but it seems the ever expanding road network only produces more traffic jams and no future rollout of public transport is catered for.
I guess one can dream.