I am also wondering this since I have a LTE-enabled camera with prepaid data on the Mint MVNO (four capital letters 𝅘𝅥𝅮) running on T-Mobile's network. My Mint account settings has no privacy controls at all, and their privacy policy only mentions “location” in terms of GeoIP while browsing their website and in terms of E911 access if you dial emergency services: https://www.mintmobile.com/privacy-policy/

I found this “Ultra Mobile and Mint Mobile – Policies regarding Geolocation Data” <https://docs.fcc.gov/public/attachments/DOC-386591A1.pdf> that mentions third-party sharing, but it's a little dated (2022):

“Describe the arrangements, agreements, and circumstances in which Ultra Mobile and Mint Mobile share subscriber geolocation data with third parties that are not law enforcement.

None. The enhanced 911 process provides subscriber geolocation from the cell phone in the event of a 911 call, but it is not controlled by Ultra or Mint Mobile. Neither Ultra nor Mint Mobile provide geolocation data to any third parties.”

What this doesn't answer, however, is what T-Mobile are doing with Mint customers' location data. I have to assume they're selling everything they can and that's why the MVNO is so cheap compared to the main brand lol

Main brand is even cheaper when you have a business account. It's only people with few lines that get railed on postpaid wireless.