I agree that they should probably say "it's a private business, it's their choice, as long as the food is labelled as halal (which it will be to reassure Muslims), there's no problem", but you might say that a Communist politician would be more likely to be get involved in such things than a right wing one, on the grounds that Communists are more happy with government-set regulations (such as the methods of slaughter). The chain's decision to offer meat slaughtered in either way seems a reasonable compromise, but I see that it came after intervention by another mayor.
And no, it's not a "cross-partisan front to emulate Tea Party". It's about this issue, and she's a Communist, and we know there was a Socialist mayor in one of the towns. That makes it cross party, but it doesn't make it a Tea Party.
There is a row in Harrow in North London, where the contractor that supplies school meals uses only halal meat:
http://www.bbc.co.uk/news/uk-england-london-10884787http://www.harrowtimes.co.uk/news/8421942.Council_urges_schools_to_consider_non_Halal_option/And notice that, in the case of the schools, the Muslim spokesmen say there should still be non-halal meat available for non-Muslims. That, of course, is a school, where there isn't a choice of going to a competitor down the street, so it's a bit different. But they do recognise that some people want meat that is non-halal.