Northeast - No road bikes for Hub on Wheels in Boston??

The Hub on Wheels (www.hubonwheels.org) is a 25-mile ride through Boston to benefit Boston's Digital Bridge Foundation, which helps educate Boston schoolchildren about technology. I was planning to register and ride when I read this (http://www.hubonwheels.org/infowhat.html): "A hybrid or mountain bike is preferable. The route goes on some bike paths and unpaved sections that are not ideal for road bikes."

1. Has anyone ridden in this event before? Is this statement true, or is it included out of an abundance of caution, etc? (I'm new to the Boston area and don't actually know if this ride is an annual event.)

2. Can anyone surmise how much of the ride is "off-road," or easy/hard it would be to avoid these sections with a detour? I'm riding a new road bike and I'm still a little OCD about taking it on unpaved paths. Route can be found at http://www.hubonwheels.org/map/.

3. Is anyone planning to register and ride?

Thanks in advance for any information/help!

1. Has anyone ridden in this event before? Is this statement true, or is it included out of an abundance of caution, etc? (I'm new to the Boston area and don't actually know if this ride is an annual event.)

I haven't ridden in the event, but I've ridden most of the route that they show on the map, and I can certainly believe that there are parts of it on gravel paths (parts of the Emerald Necklace, Franklin Park, etc.). It's not singletrack but it's not paved, either. Another consideration is that a lot of it is on paths (they're sure not taking over the J-Way, sigh), and there will be a lot of people, so getting crowded off onto the grass/dirt/doodoo is always a possibility. If I participate, I'll be riding my Urban Assault Vehicle rather than the roadie (although I'd love to take the roadie down Storrow Drive!).

Thanks for the fast response and the helpful information. Is anyone planning to ride in this?