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.
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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.