I outlined the lowbeam relays and bulbs in red.
See how the main body ECU connects to the relays? Those are the ground terminals for the relays' coils,these are low-current circuits. The ECU does not look for a 55-watt load,hence no difference in operation if a HID ballast replaces the bulb. There's no need for "special ballasts",resistors,etc.
The diagram also shows the highbeam circuit,you can see the DRL relay. According to Toyota it's a solid-state relay,I think it lowers bulb voltage via pulsewidth modulation instead of resistors.