There's a public set of first responder guides with detailed diagrams for every make and model available. While I'm not sure they have a hotline, Tesla has always tried very hard to provide accurate information how to douse flames, which cables to cut to render the HV system disabled, and how to take care to ensure the car doesn't reignite. See: https://www.tesla.com/firstresponders (e.g., a specific guide: https://www.tesla.com/sites/default/files/downloads/2016_Mod...)