Video of one such ticketing: http://www.archive.org/details/cm29-8-08ticket
During rides the police often annoyingly block the front with their bikes at intersections, to allow their van and stragglers to catch up and to keep the Mass in one tight, slow ride. Part of this compacting process involves being instructed by police to go through red lights, despite pedestrians having to wait to cross. So, how strange is it then that the police were picking on some riders and ticketing them with a fine for going through red lights? Another rider was stop and searched for drugs and another threated with arrest for not giving ID.
Two very good websites for legal advice are...
For particular page regarding stop and searches see...
These website also have some useful links about legal related stuff.
I am just a legal novice so please add to this if you know more, or about any recent changes to the law. The sites mentioned have good info though so read if you want some more clarity on the matter.