The police can show up and search your premises on one measly anonymous tip. Happened to me in 2002. It wasn’t for a drug tip, it was for a “she’s running an illegal office” tip (if you can believe that). The cops were pretty embarassed when I opened the door with my hair not yet combed and it was obvious that it was an apartment, not a translation company premises, but I made them come in and search everything to ensure that no one could say there was a miniature Berlitz underneath the dirty laundry.
Get it through your head: You have no rights. Doesn’t matter if it has to do with drugs, economic activities or just being too loud. In actual practice, any Taiwanese who calls you in will probably be heard and get action. The police refused to say who had tipped them, too, although given other events at that time it soon became obvious.
The time I had to get police action on someone, it took me a half-hour of debate-type conversation to get them to even take me seriously. I doubt the folks who sicced the police on me had that problem.