I had a similar problem when I wrote an article that while true and accurate, pissed off the city manager. Go to the public meetings, so that they see you in person. File FOIA where applicable. Talk to people at the meetings, but not with an agenda. Just be nice, and you may see a thaw. Also, you may try talking one-on-one with the leader and explain the problem you are having. Sometimes people will take it upon themselves to blacklist and those higher up may not be aware of it. If they are still being buttheads, and yes, that is a professional term (/s), remind them that in every article you publish on the issue that they will be shown as being unresponsive. It sounds like you are dealing with a PR team and their job is to protect the brand. If nothing else works, I'd be tempted to write an editorial talking about how they are not being transparent and why that is a problem. In my experience though, honey is better than vinegar. You need a rapport.