that's right - it's Tradest Indicator Script from https://tradest.io/

I'm trading with it for a while. For alerts you can set them on TradingView for each buy sell signal on each time frame. Alerts of course can pop up on mobile app (if you're logged in same account) or by email depends on setting on TradingView.

I believe Telegram signals is a separate service they provide if someone is not familiar with script implementation on TradingView - as all signals are coming from the script anyway.