No, the messages are not encrypted, they are only passed over SSL to prevent people in the middle from getting the messages - just as Skype does... but Tesla or

No, the messages are not encrypted, they are only passed over SSL to prevent people in the middle from getting the messages - just as Skype does... but Tesla or possibly Firebase can still read your messages if they wanted to. So you'd be just as at-risk using Tesla as you are using Skype or Google Hangouts (previous Talk).