And as First Glasgow today ended an extended public consultation, Strathclyde Partnership for Transport chairman George Redmond called the process "a sham".
Bosses at regional transport agency SPT believe they will have to dig into their dwindling budgets to save routes being dropped by the private operator.
The public consult-ation was about its biggest route changes in more than a decade.
First Glasgow is expected to start the registration process for new SimpliCITY routes with the Traffic Commissioner, its main watchdog, on Friday.
That means SPT –which subsidises routes bus firms such as First say are loss-making – has just two days to try to influence the process.
But officials have already worked out they will have to find at least an extra £500,000 to cover routes currently scheduled to be dropped by First, including some to Southern General and Gartnavel hospitals.
SPT chairman and city councillor George Redmond said: "We have been informed that First will begin formal registration of their new services this Friday – only 48 hours after the public consult-ation on the biggest service changes in more than a decade closes.
"How can First poss-ibly condense public opinion within such a limited deadline? How can SPT possibly consider the impact of this within the same time frame? It is ridiculous to suggest we can hold meaningful discussions on the con-sequences of all these changes in two days.
"All we know for a fact is outline proposals show serious reductions in frequency of services and the complete withdrawal of others.
"Passengers in Drum-chapel, Cambuslang, Cumbernauld and Glasgow's West End will undoubtedly suffer.
"Our early estimates – and these figures could rise – is that an additional £500,000 will be needed to subsidise replacement services.
"That's on top of the £11million SPT spends each year on socially necessary bus services.
"Finding half a million pounds from public funds will have a direct effect on our other transport services."
First Glasgow managing director Ronnie Park said it had been monitoring feed-back during the consul-tation and "reviewing our plans accordingly".
He added: "Whilst we've not made any final decisions, we have a good understanding, as we approach the end of the consultation, of how we can take our plans forward and deliver a significantly better network for the majority of customers.
"Over the next few days we will be reviewing all the feedback again ahead of submitting proposals for SimpliCITY to SPT.
"There remains plenty of scope to take on board the views of SPT before submitting our final proposals to the Traffic Commissioner later this month."