I applied in late August and a recruiter called me up in mid-September saying they wanted to fly me out to site in California. I flew in in early October, spent a night at a hotel, then had an hour(ish) interview with a hiring manager and two engineers the next day (Monday -> Tuesday). It wasn't a formal interview of any sorts - if you have enough to talk about, you can simply rely on explaining your past experience for that hour. They are interested in what you have to bring to the table.
The interviews are traditionally STAR (from what I have read) ,but the interview I had was much more informal, and I spent awhile just talking about my experience, which was cool. To prepare, I would recommend simply reviewing your resume and knowing all your projects inside and out.
I flew out the same day as the interview. I had a wonderful experience talking to them and the flight/hotel/rental car reservations went very smoothly.
Overall, they seem to have their interview process down to a tee. I applaud their HR team for the effort.