I don't think it's appropriate for the emergency services to promote the use of W3W to the general public. Nor do I think it's appropriate for them to advertise it. It's also inappropriate for critical applications at the moment.

The initial blog explaining the risks of emergency services using W3W Why What3Words is not suitable for safety critical applications: https://cybergibbons.com/security-2/why-what3words-is-not-suitable-for-safety-critical-applications/

Article about the legal threats against Aaron Toponce a security researcher. https://www.techdirt.com/articles/20210430/22510246716/

Public Money Public Code campaign. https://publiccode.eu/

Further Reading. What3words and Homophones: https://emergencylocate.co.uk/w3w_hp_blog.html

App used by emergency services under scrutiny: https://www.bbc.co.uk/news/technology-56901363

What3Words submitting takedown requests against Tweets: https://news.ycombinator.com/item?id=21184505

Post by Terence Eden about What 3 words in 2019 https://shkspr.mobi/blog/2019/03/why-bother-with-what-three-words/