In the Twin Cities, if you go to a meeting at someone else's invitation, and parking is not free, you can often get it validated by the inviting agency. The Center for Transportation Studies often does this for guests at its meetings on campus. The Metropolitan Council does this for their meetings at their HQ in St. Paul.
However if you arrive by transit, you cannot get your parking validated, as you did not park at your destination. I have complained about this for a while, and the last couple of meetings, the Metropolitan Council (also the region's transit operator) has sent me transit passes in the mail. Thank you Met Council. This should be standard practice, and given at the time of the meeting, in the same breath as "do you need your parking validated" they should ask "or a transit pass". Especially if your goal is to increase regional transit use, it seems obvious you should not subsidize its competitor.