The IWCA are an active day to day, week to week organisation composed of local working people. It's this day to day work that has brought then success and one of those successes has been the election locally of IWCA councillors, where local workers have decided to endorse this work rather than back Labour or the Lib Dems.
I would suggets the litmus test for the IWCA is the winning of the day to day issues not the getting elected. After the last by election there was a an interesting and informative discussion on the election result and one of the conclusions was that it was the day to day stuff that had to have priority.
Standing in elections imo is a tactical question and not one of principal.
In terms of the tradition of local workers organising to tackle local issues then I think you can find better examples than the bloody Lib Dems whose political tradition and legacy includes the Isle of Dogs, Cyril Smith and the very right wing pre Militant Council in Liverpool. Even in the North West where they are gaining a toe hold their record in Stockport for example includes closure of the local swimming baths in one of the most deprived ares, the closure of the local library in the second most deprived area and the recent clisore of something like ten primary schools.
The CP campaigns for local housing in the thirties and fourties are a much better example imo. The recent defend local Council Housing campaigns and the campaigns against gentrification are issues that the Lid Dems wouldn't touch with a barge pole.