That is true of Hyde Park vs Fairmont, but Readville is Zone 2 in both lines.
Zone 2 is $217. 75/month, so pretty close to Zone 1, but still, my point is that they would have already been going to Fairmont to save well over $100 a month anyways - Fairmont being Zone 1a isn't that new of a thing anymore.
I think the real question is as simple as: "What were ridership numbers in the two weeks that FOLLOWED the free trial? Did free trials produce a lasting change in behavior?"
All we know is that the free trial is some kind of upper bound on ridership ("how many would ride transit if it were free?"...though I suppose if we paid people to ride it could go higher ;-)
So I would have liked the free trial to have continued until free ridership leveled off (growing by, say <5%/wk) ...a sign that everyone who might be induced/educated had, in fact, tried it.
For now all we know is that by week 2 we'd changed behavior & educated twice as many people as week 1 did...how much further could it have pressed?
I think one needs to also take into account the lack of being able to normally easily transfer. Right now, without a monthly pass (either ticker or card), you have to basically pay double the subway/bus fair to get to South Station and then transfer to the Red Line/Silver Line/etc, whereas the existing bus service, while slower, gives you that free transfer, so $2.25 vs $4.50 one way - on the round trip you save almost 5 bucks not taking the Fairmont Line. Also, the ticketing (without a monthly) is also annoying on the CR, since a normal Charlie Card cannot be used, and one needs to either purchase on train, via the app, etc.
My question is, how much of an impact was not not so much in making it free, but, in making it that much easier to use, as now it was the same price as the bus (with transfers), and, it took away the less than ideal payment options to use the service.