All in all, I think that a small investment in new roads - I'd personally prefer the more modest "scenario 1," which will cost less and induce less additional traffic - would be more than worth it if building them forces these suburban communities to grow in more sensible, sustainable patterns and invest in transit.
And the beauty of this plan is that it makes a tight case that new roads should not be built without first undertaking new "smart growth" measures to focus growth into village centers, and building new transit lines. Transportation advocates now have an even stronger case to make to re-allocate funds that the Maine DOT and the Turnpike Authority had planned to use on wider roads, and use them for better transit instead in the short term (and it helps that the argument comes from a study that was actually funded, at considerable expense, by those anti-transit agencies).
But the study's approach also has a major pitfall. If the region needs smarter growth, AND a big expansion in transit services, AND a handful of new roadway and freight rail projects, AND for all these things to happen more or less simultaneously, then how is that going to happen? How do you coordinate four to seven different municipal governments (South Portland, Scarborough, Westbrook, Gorham, plus the outer suburbs of Standish, Buxton, and Hollis) so that they agree to focus their growth in specific areas and provide local funds for better transit services? How is the region going to pay for $80-$100 million worth of road improvements, plus $40-$50 million for new buses and rail line upgrades? And how's all of this going to happen in a coordinated fashion?
I think that the region is going to need a relatively strong new finance and oversight authority, possibly funded through new tolls, to ensure that the municipalities stick with the plan. Funding for transportation improvements should only happen if the entire region can be assured that its investment won't be ruined by sprawl commuters from a renegade suburb that refuses to focus its growth. And this finance authority should also be structured such that it focuses its investments on better transit service, before it starts building roads.
Will suburban politicians agree to turn over a measure of their autonomy to what would effectively be a new regional government? That seems like a big "if." But the alternative - wasting thousands of hours every day in stop-and-go traffic - is almost certainly less appealing to the residents of those towns. The question is whether suburban town managers and officials can swallow their "local control" pride and lust for new roads in favor of a smarter, more sustainable regional solution.