The 2015 Minnesota Plumbing Code makes it very clear... Cities, Property Owners, Plumbing Contractors and Backflow Testers all have responsibilities when it comes to preventing backflow.  

It's simple, do your part, or suffer potential punishment (especially if a backflow event occurs).  While multiple parties play a role in keep our drinking water safe, cities must ultimately be the leader to enforce the Code.  If cities fail to develop a backflow prevention program, health, legal and financial impacts can be substantial to the city.