I live in Tahoe (with an 85D). First, the car is absolutely solid driving on ice and snow. I have never felt it slip. It feels like it's driving on dry pavement! The combination of low center of gravity and central mass with traction/stability control makes the car perfect for snow. I have air suspension and it's helpful to raise it in deep, rutted snow.
Second, chain control. Most of the time it's R1 (sometimes R2) which is 4WD with snow tires (or chains on 2WD). You need to have good tread on your tires. They don't read the sidewall but just look at the tread. They probably won't recognize your Tesla as 4WD so just roll down the window and tell the inspector that it's 4WD... that works for me. You're supposed to carry chains but they never check... I used to carry an old set of chains (that didn't fit the car) in my other 4WD cars just in case they checked but they never did. If it's R3, you'll need chains but that is rare (and only for a short time) and you really don't want to be on the road in any vehicle with R3.
TYPES OF CHAIN CONTROLS:
During the winter months, motorists may encounter traction chain controls in the mountain areas within California.
When chain controls are established, signs will be posted along the road indicating the type of requirement. There are three requirements in California.
Requirement One (R1): Chains, traction devices or snow tires are required on the drive axle of all vehicles except four wheel/ all wheel drive vehicles.
Requirement Two (R2): Chains or traction devices are required on all vehicles except four wheel/ all wheel drive vehicles with snow-tread tires on all four wheels.
(NOTE: Four wheel/all wheel drive vehicles must carry traction devices in chain control areas.)
Requirement Three (R3): Chains or traction devices are required on all vehicles, no exceptions.