It's just branding, because it's a shuttle service between a mainline stop in a nearby village and their Gigafactory outside Berlin.
The best part is that this train isn't made by Tesla, it's just them leasing battery trains from Siemens, and they don't even operate them:
Tesla plans to switch to operating battery-electric trains from the Mireo Smart family, manufactured by Siemens, replacing diesel trains currently transporting employees to their factory near Berlin.
[...]
The trains will be leased from the newly established leasing company, Smart Train Lease, founded by Siemens in early 2024. The operation of the trains will continue to be managed by the passenger transport operator Niederbarnimer Eisenbahn (NEB).
Source: https://www.railway.supply/en/tesla-is-transitioning-to-environmentally-friendly-trains/