I think it is pretty common that mobile phone systems go down or work poorly during large scale protests. But also during music festivals. So I think the mayor part of phone services going down is lack of overcapacity, when you collect lots more people in an area then the mobile phone system is designed for.

That does not stop your mobile phone from working as a recorder however, and you can after leaving the affected area send the film.

Sweden's finest (and perhaps only) collaborative, leftist e-newspaper Synapze.se