It completely depends on the company. Some companies verify, others don't.

I have geico car insurance and travelers home owners insurance. A representative from travelers actually came out to my house and 'surveyed' the area.

Home ownership is easily verifiable via the property tax websites.

If you're talking about, specifically, the Progressive discount for owning your own home, they'll want a copy of your property tax bill or homeowners insurance policy.

Most companies give you a discount if you have your homeowners or renters insurance with the same company that has your auto insurance.

You cannot just own a home. You have to have the both insurance policies with the same company.

At the beginning they do, but usually, the discount only comes into play when you get both auto and home owners insurance through the same company. If they provide the discount just for owning the home, they will probably call the tax assessor's office at some point to verify your ownership.

Doesn't matter if you own your home (make no mortgage payment), "own" your home (make a mortgage payment), or rent.
As long as you have an address and you are living there, you get a discount on your auto insurance. But only if your home owner's insurance & auto insurance are from the same insurance company.

We have renters insurance & auto insurance with the same company and get a discount.