"His condition is serious and he is in intensive care in Wellington hospital," Marko Bogoievski, Infratil chief executive, said in a statement. "All our thoughts and prayers are with Tim and his family at this time."
The Wellington-based company acquired NZ Bus 2005 for $252 million. NZ Bus is New Zealand's largest public transport operator with bus services in the Auckland and Wellington. It has about 1,000 buses and 2,000 employees.
It is the second blow for Infratil this year, after company founder Lloyd Morrison died after a long illness in February, aged 54.
It is also latest in a series of incidents where passengers have been hit by buses in central Wellington.
A witness told Fairfax Media Mr Brown went under the front wheel and the first of the rear wheels of the bus.
"The bus stopped and he was jammed between the two wheels so people tried to pull him out of there and applied CPR," Graham McCready said.
Mr McCready said road works on Willis St could have contributed to the crash as there are not many places to cross.
- with BusinessDesk