The Massachusetts Bay Transportation Authority has hired a consultant to explore additional possibilities for outsourcing by the Boston-area transit system.
Among other things, the nearly $1 million contract approved last month asks McKinsey & Company to determine if there is a "viable external market'' for bus operations and maintenance.
Privatization has become a volatile issue for the MBTA, which has been plagued by chronic operating deficits and has billions of dollars in unmet maintenance needs.
The T's control board recently hired an outside vendor to take over the agency's "money room,'' after an audit revealed security lapses at the cash-counting facility.
Hours before that vote, seven officials of the MBTA's largest employee's union were arrested on unlawful assembly charges during a protest against privatization.