Here in Ontario, you never ever saw anything on the ROW of provincial highways other than highway signs. Then the province realized that they had an untapped cash cow sitting there, and in the name of "traveller information" signed up a private firm to sell "directional" signage to anybody and everybody who was interested. Now the ROW is literally covered with signs directing to you to restaurants, golf courses, bingo halls, etc.
The province gave this same firm the authority to deal with counties/municipalities to extend signage from provincial highways to local roads. When I worked in Sudbury, we told them to take a flying leap when we saw what they were proposing to do. Basically, they wanted unfettered access to our ROW to put up as many directional signs as they could sell (without consulting or reimbursing us). We told them we had our own policies and that they could very nicely go to hell.
The Region provides tourism directional signage to establishments that meet set criteria. The signage is provided by the applicant - the Region installs and maintains the signs for a set fee. Very strict enforcement - I had to turn down the trout farm/driving range/cross-country ski lodge/general store.