I'm looking to establish the most effective communication strategies for disseminating crucial information (such as road closures, weather updates, and active shooter alerts) to airport stakeholders, including Uber drivers, skycaps, security personnel, public works, and contractors. - Is Everbridge and Microsoft Teams viable for these types of communications? - What are the best practices or other recommended platforms for ensuring rapid and reliable communication in such scenarios?

Everbridge is a viable option.  We used it in the past.  But we recently switched it over to Alert Media instead for cost saving. 

Text messages will be your best option to cover such a wide audience range. MIR3 is a great product for this.

It is not entirely clear from your question whether you want push notifications (i.e. one-way) or bi-directional (two-way) communications, but I am going to assume the previous.

Tools like Microsoft Teams are not great at push notifications in my experience and are dependent on a data connection, be that Wi-Fi or mobile data network (cellular). This could also prove quite an expensive option from a licensing perspective.

For me, a mass notification system is principally about:

1. The different methods of communication it supports, for example, can I send SMS if the user has no data connection?

2. The integration with whatever other communications tools that you are using, so that information can be shared regularly and easily.

3. Security controls and logs around who can send messages.

4. From a DR scenario, you might also want to ensure that the tooling can be accessed and used without reliance on your corporate infrastructure (although this may not be relevant in your scenario).

So in summary, I would recommend some form of Mass Notification Service rather than a more generic communications service such as Teams. I don't have any direct experience of Everbridge, so cannot guide on that specific product.