I just finished the 4 day tour sponsored by Mass Bike, the same organization that is doing Hub on Wheels. I would say that they are trying to attract "recreational" cyclists to this. I didn't do it last year because of the dirt/ unpaved issue. I would never ride my road bike in Boston! I bought a hybrid last winter, but still not sure if I would do this ride because I don't think the speed I go on the hybrid would qualify me to be up front; it weighs about 28 lbs with the bag on it. As I said, doing this on my road bike is not an option.
I also found that the tour I did didn't really mention the difficulty level of the rides. There were 30, 50, 65 mile routes each day and while the elevation from point to point was on there, they should have been more up front about how challenging this tour would be. We knew it would be challenging, but a lot of people didn't. And the shorter rides weren't much easier than the longer ones.
So, this makes me a bit uneasy about doing Hub on Wheels. Mass Bike is a great organization, but I think they need to look at safety from a different angle.