"We look forward to presenting our case to affirm the right of all to express such viewpoints in the public square," Fiorentino said in a statement.
The archdiocese has made a separate agreement to place similar ads on the District of Columbia's bus shelters, whose advertising is operated by Clear Channel Outdoor. These ads contain a Bible verse.
McFadden said the archdiocese has been using bus ads for major campaigns for close to ten years. City traffic creates a "captive audience" and the buses tend to go into areas that lack bus shelters.
"This is our best way to reach different communities where other forms of media aren't necessarily available on the street," he said. The campaign strategy promotes ads on multiple platforms to remind people about Christmas and perhaps encourage them to go to Christmas Mass or volunteer to help others.
In McFadden's view, the proposed WMATA ad was "comparatively mild" in terms of promulgating religion.
"This ad campaign is really just as much about the joy of the holiday season, reminding people why we do what we do, but also giving them the option to help their neighbor through various volunteer efforts," he said. "This wasn't simply about going back to Mass, this was also about trying to be a positive voice in the community at the time when we probably need it."
Susan Timoney, secretary for pastoral ministry and social concerns for the archdiocese, was among those who helped develop the campaign.
"Our ad was designed to be placed on metro bus exteriors to reach the broadest audience and to invite everyone to experience the well-accepted joyful spirit of the season, or to share their many blessings with others less fortunate through service opportunities," she said.
Timoney said the archdiocese wanted to encourage society to help care for "our most vulnerable neighbors," to "share our blessings," and to "welcome all who wish to hear the Good News."