Builder Leszek Soltysiak suffered severe injuries after being pushed 15 metres along the Euston Road by the bus.
He was part of a two-man team brought in by Galliford Try to fix snagging issues at the St Pancras Renaissance Hotel and Chambers where the firm was in charge of a £103m restoration project.
Westminster Magistrates’ Court heard the firm arranged for two workers from the logistics team to remove tape from the outside of an apartment window on the third floor of the residential block in the early hours of March 4 2011.
As scaffolding had been removed from the site, the men had to move a cherry picker from a compound in Euston Road to another in Midland Road to enable them to carry out the job.
Soltysiak began to reverse the machine out of the exit onto Euston Road, raising his operator platform to clear the fencing.
Deciding it was clear, he continued backing out unaware that a double-decker bus had just turned into the road.
The second worker waved at the bus to try to get it to stop but it was dark and the bus driver saw nothing.
The top of the bus hit the operator platform overhanging the road forcing the jib to slew across and hit a brick gate post. The collision catapulted the driver from the platform and he fell to the ground in front of the still moving bus.
The bus driver braked, thinking he had hit a tree and stopped about 15 metres further along.
Soltysiak was found partially underneath the front nearside. He suffered serious head, arm, pelvis and leg injuries and was only able to return to work earlier this year.
HSE’s investigation found the incident could have been avoided if Galliford Try had fulfilled their duty to properly plan and supervise the work.
After the hearing yesterday HSE Inspector Paul Hems said: “This worker narrowly escaped death after a series of events which almost seem unbelievable but in fact could have proved fatal.
“A 14-metres long slow-moving machine, not suitable for use on a public highway, was moved against the flow of traffic on to a three-lane road.
“Both workers were without high visibility clothing and there were no visible warning lights on the cherry-picker despite it being early morning and still dark which made it, and the men, effectively invisible to the bus driver.
“The dangers involved using cherry-pickers are well known and yet the company failed to ensure safe movement of the vehicle between different compounds at the site.”
Galliford Try pleaded guilty to safety breaches and was fined a total of £12,000 and ordered to pay full costs of £16,459.70.