Lowering one's expenses on public transport

I was quite stunned to see a guy come through the electronic ticket barrier at my local station this morning and hand his ticket to another guy waiting there who immediately went back through the barrier to catch a train. Weekly tickets here in Sydney allow unlimited journeys through the rail system within the zone for the ticket.

I don't know how these guys linked up but I could easily see it happening via Facebook or whatever. If you could arrange your starting and stopping times at work or wherever you could share the cost of a weekly ticket amongst a crowd of people, all of it legal (well probably not within the T&C for the ticket but how are you going to check?). No doubt the rail management hate it but how are they going to stop this happening?

I wonder if there is already an online 'ticket pooling' service, like car-pooling but you share your weekly/monthly/yearly ticket. Let the computer work out how to allocate people to a ticket. It would require incredible discipline but if you are struggling for every dollar, you need such discipline to survive. (I remember the luxury when I first started to earn a pay-packet of deliberately not budgeting when I went supermarket shopping. Being from a single-parent family and not rich, my job each Wednesday night was to scan the newspaper for specials at the various supermarkets at the local shopping mall. I then worked out the shopping lists for each store and my mother, sister and I shared the shopping load. It halved our food expenses but it was very time consuming.)