Aluminum is perfectly fine as a conductor, and perfectly safe. In the USA, we've used aluminum for most of our power transmission and distribution since the beginning of "the grid". Everything from the power plant to the meter at your home is connected with aluminum.
Where aluminum causes fires is due to the fact that it expands and contracts more than copper does, and it can oxidize and corrode when not properly cared for (for example, when dissimilar metals are used, or when exposed aluminum wire ends are not properly coated).
We can assume that someone at Tesla is familiar with the properties of aluminum and can insure that they are using the right connectors to mitigate these issues. (or at least, we can hope)
The other problem in house wiring is that when you tighten down the screw to attach the aluminum wire to the terminal, the aluminum work hardens, and expansion/contraction/vibration will cause it to break.
Where aluminum causes fires is due to the fact that it expands and contracts more than copper does, and it can oxidize and corrode when not properly cared for (for example, when dissimilar metals are used, or when exposed aluminum wire ends are not properly coated).
We can assume that someone at Tesla is familiar with the properties of aluminum and can insure that they are using the right connectors to mitigate these issues. (or at least, we can hope)