There may still be occasions on which photographers in the Square will need to stand their ground. The notice states that "this permission is limited to hand carried, self supported equipment" and expects photographers to comply with Wardens' "reasonable instructions" in relation to the health, safety and welfare of people in the Square." The key word is "reasonable" - and there's a number to contact if the instructions start to get unreasonable. Parliament Square Gardens - subject to the same byelaws - are also mentioned by name in the notice.
Meanwhile in Bristol, the Bristol Film Office, following a very positive meeting with NUJ Bristol Branch, have confirmed that "media press (news) film and photography crews are not required to apply for permission to film" on Council land and property. See www.londonfreelance.org/fl/1203bfo.html