Kay said a decision on whether the Purple Line can move to the next stage is likely to come later this summer.
Canton resident Rosenberg said he's confident that opponents will ultimately block the project when it comes time to come up with the money for construction.
"The time really is on our side and not on the side of the people who have been promoting this," he said. "Until somebody finds $2 billion, obviously this thing's not going to be built."
Construction of a new transit line with federal assistance is a laborious, drawn-out process involving minute examination of a local agency's plans, costs, projected revenues and ridership assumptions. Approvals can take many years.
The Red Line planning process was in the works for several years before public hearings on alternatives were held in 2008. In 2009, O'Malley made the final decision to build a light rail line instead of a rapid-bus alternative. Proposals for more extensive tunneling were scrapped because the costs would have exceeded federal limits.
According to the MTA, if the project clears the remaining hurdles and federal and state funding is available, it would take until about 2020 to complete the Red Line.
Kay said the PE process would bring the planning to the point where it is about 60 percent complete and ready to move into the final design phase. By the time preliminary engineering is done, such things as the design of the stations and the appearance of the train cars should be known, he said.
The federal approval comes as work is progressing on such matters as design of the 20 proposed stations on the Red Line. The MTA has 17 Station Area Advisory Committees, made up of an estimated 250 volunteers, working on things such as platform location and pedestrian access.
Engineers under contract with the state have also been contacting homeowners in some of the neighborhoods along the path of the Red Line, asking for access to their basements to determine whether tunneling could cause any problems.
Kay said the MTA needs to know how deep the basements go in some older neighborhoods such as Fells Point and Canton, where many homes don't have construction plans on file with the city. He said that such inspections are voluntary and that the MTA does not need access to every home.
The MTA does not expect tunneling to have an impact on existing buildings, Kay said. He said the average tunnel depth would be 40 to 50 feet below ground. That is comparable to the depth of the Metro tunnel under neighborhoods such as Upton and Bolton Hill, he added.
Kay said that in his many years at the MTA, he has never heard complaints about noise or vibrations caused by the subway.