I have not looked into the correlation, so I do not know if there is any evidence of this whatsoever. Also, I imagine that the facts may be complicated by the ruling party and the political allegiance of the Mayor of London, which may not be the same.

However, if there was correlation, I imagine it more likely that Unions would have previously used their political influence to dissuade reforms from being proposed by politicians in the first place thereby removing any need for them to strike.