there have been groups have whinged about, the money can be better spent, eg hospitals etc
people will whinge about the new stadium, then once built think its the greatest thing since electricity!
Some people will always whinge. But I don''t think it goes along party political lines in this case.
By the way, the track and signalling improvements will benefit normal peak hour services on a daily basis as well as when the stadium is in operation. So there is some positive side-effect.