Do remember that the fares on the line can only increase in line with 'protected fares' rules though. The price changes brought about in 2008 on the SVB Line were allowed by the DfT as a special case. The RPI+n% formula still applies though to the SDR, it just hasn't been used in January 2009/10/11/12.
Since the introduction of the 'zonal' fares on the SVB Beach Line in 2008, the fares have been held.
If they had increased by the RPI+n% formula, the fare from Severn Beach (currently £3.00 SDR. 2008 £3.70) would now be £4.40. The fare from Clifton Down (currently £2.00 SDR. 2008 £1.60) would now be £1.90.
The 'zonal' fares, when introduced, saw some winners but mostly losers. SDRs from Clifton Down/Redland to Bristol TM were £1.60 and a CDR was £1.50. Now the fares are £2.00 SDR with no CDR. From Severn Beach it was £3.70/£3.40. Now £3.00 SDR only. Undoubtedly Clifton Down has far more pax than Severn Beach, so farebox revenue increased considerably under the 'zonal' system from there. The 7DS increased by 50% from £4.00 to £6.00!
If the old fares had stayed in place and risen by RPI+n% yearly, pax from Clifton Down/Redland would still be paying less than they are today. Particularly if they buy 7DS. The SDR fares from closer in (Stapleton Road/Lawrence Hill) doubled under the new 'zonal' system. The busiest parts of the line saw increases with the new fare structure, way beyond the RPI+n%.
As these figures demonstrate, the subsidy was never really about fares, it was provided to increase service provision.
What has happened though is Clifton Down/Redland folk now pay more than they would've done under the old fares, whilst the far fewer pax out my way (Sea Mills - Severn Beach) pay less. So, arguably it's the passengers subsidising other passengers rather than the City Council directly subsidising fares. That seems to me to be a neat solution, the new structure reduced fares for far fewer people than it increased. But then I would say that. In real terms my fare from Shirehampton dropped, more so as I hold a railcard with allows 50% off on SVB Line fares!