Issues (technical setbacks and criticisms) needs to be checked for NPOV and verifiability.
Has it actually been used by the police yet to trace movements? (Security services unlikely to confirm or deny.) What is the official policy regarding this?
The PAYG system changed in November so £4 (£5 on specific NR journeys) is debited at start of journey and the difference is credited back at the end. This applies a maximum cash fare to those who do not touch out.
Bus passes bought at tube stations are only on Oyster soon (there is a poster). Need to find details for citation.