In talking to the reps from one of these organizations, they come to town and first check the entertainment section of the local paper and any entertainment guides...those little magazines found in the lobby of many establishments. They check out any places listed in these publications. And they check out any web-based entertainment guides. Then, they drive around looking at billboards and entrance signs for entertainment notices.
For years, I played an upscale restaurant (14 years, actually) and told the owners to not use the "week-ender" (a listing of entertainment venues in the local paper) to publicize the music. We had no problem. The year I left, a musician called in his own listing. Within weeks, all liscensing organizations had contacted the place. They now pay a total of $2750 a year for each of the two places they own.
In the case of the little restaurant I just left, the reps of the liscensing company were talking to the owners of a bar in the same shopping center. The bar owners said "there's a piano player at (restaurant name). Are you collecting fees from them"? Guess what? They went right down the street and the rest is history. This is about the 9th time music was discontinued at a place I worked as a result of actions like this.
R.