Depending on the size of the town / city, it could be trivial. There's ~6 companies doing electrical work in my town. Not only are they commented on / recommended on local social media, they see each other's quotes all the time when people compare prices. If someone started a new business, I suspect they'd all know within days/weeks.

From other specialist non-trade business I'm familiar with, people are normally aware of new employees coming to town before they even start working. People talk to each other.