Disappointing news: spoke to the point of contact for PG flying from Mammoth Mountain Summit (at the resort), and this privilege has been recently revoked. Last I inquired, there were a few hoops to jump through, but provided you did that and lucked out on weather, you could take the cable car up and have a sledder with great views. Sounds like that won’t be possible for the forseeable future – have to stick to the other options in the area.