Wow. I have been lurking for almost 10 years, and this is the post that made me sign up.
I can actually directly address the OP’s concerns - I am a University professor who has worked with BSL2 and BSL3 arthropod-transmitted pathogens for over 10 years. The first thing to realize is that BSL3 labs are very common – any medical school or even decent University microbiology department will have the capability to work under level 3 conditions. The things in these level 3 labs are not THAT nasty – the increased biosafety level is to protect the workers, not really to protect the public. In most cases, the pathogens they are working with are circulating in the wild, maybe in your backyard.
Your vector control district almost certainly wants a level 3 lab to do their own West Nile virus (WNV) isolations. It is barely possible that they also want the ability to work with chikengunya virus (CHIK isn’t here yet but it probably will be within the next 5-10 years, and will make WNV look like nothing). If they are working with WNV, I, as a resident, wouldn’t worry at all – you have orders of magnitude greater chance of being exposed by mosquito bite in your own back yard. In fact, chances are pretty good that you have already been infected and never knew it.
Now, whether your local vector control district SHOULD have a level 3 lab is a different question. Some states have very well qualified mosquito abatement and vector control programs (California and New Jersey come to mind) – in these states, SOME districts have significant research programs and have PhD-level scientists (including virologists) on staff. Does yours? I don’t know.
If the level 3 lab isn’t working on Select Agent pathogens (WNV is not a select agent) then the certification is easier (you need CDC and sometimes USDA certification). The paperwork in a bit of a bitch, but it always is. If select agents are being worked on (or even just housed there) then you get into much more detailed Federal oversight including FBI background checks, security clearances etc…
The hairy stuff is Biosafety level 4. There are only a few BSL4 labs in the country. Very few people are rated and certified to work in BSL4 conditions. I am not BSL4 certified, and have no intention of ever doing it, but am familiar with how they are designed. I have also had the unique privilege of touring a BSL4 lab that was not “hot” – and I needed to pass a criminal background check just to get into the building lobby.
Without saying too much, I can tell you that there has never been a release of an agent from a BSL4 lab. Because of the way they are designed, coupled with the safety procedures, training and background checks under which they run, I will say it is effectively impossible for an agent to be accidentally or even deliberately released.
So don’t worry about your local BSL3 lab.