Your comment Richard was a general one that it is impossible to achieve precise running times in mixed traffic, without being limited to Melbourne. Those European systems once suffered (and some still do) Melbourne's problem. The lesson to draw is that it requires an integrated road and traffic management approach to ensure that PT services do run on time.
There is an ongoing theme here of government fining operators for something that is caused by government inaction and contractors should be seeking to better define this issue before signing on the dotted line. Perhaps they're so desperate to win the contract that they're prepared to wear this risk and factor the fines into the contract price.