My name is Dr Margriet Dogterom and am the founder and owner of Beediverse. I write this blog for all who love bees and who want to learn more about these wonderful creatures.
Community gardens are growing in numbers both in cities and small towns and so is the idea of having mason bees. These are exciting projects and are a boon to educating a large number of people about gardening and keeping mason bees. The Environmental Youth Alliance of BC (EYA), based in Vancouver, focus on educating youth and the public about the importance of bees. http://www.eya.ca/pollinators-paradise.html
Others groups focus on How-to grow food.
These groups have the same issues when setting mason bees into public spaces.
EYA involved youth to build Shelters for their mason bees. The most fancy is the Pagoda Shelter in Stanley Park. Although I have not seen it myself-I was told that it was designed so that the Quicklock nest blocks could not be pulled out of the structure. This structure is secure. I have not heard if rain was able to run into nesting holes. Setting the pagoda at a light angle would prevent this.
EYA is also involved in educating farmers about mason bees. This field shelter placed on farmland is not so tall since it is on private property, but nests are well protected from the weather.
A combination of Quicklock -corn trays and routered wooden nesting rays are used in this project.
Although the jury is not out on this yet, it seems that if a variety of nests are used in a Shelter fewer bees are produced. It is best to use one shelter for one type of nests and not mix nest type in one shelter.