The IKEA motion sensor talks to the bulb, Home Assistant can’t receive any signals from it directly.
This means that you can’t create automations in HA based on the motion sensor alone. What you CAN do is make automations based on status of the bulb so that when the sensor triggers the bulb the bulb will in turn trigger something in HA.
The efficiency of this is dependent on how fast HA gets the status of the bulb, so your mileage will vary, but depending on what kind of automation you’re looking for it could be worth a shot…?
For whatever it’s worth, I have a IKEA motion sensor in a small room, and it works flawlessly.