Hello Martyn,
The Carrera track is all outdoors and most of it has been for more than 10 years. The only bit that is not out there 24/7 is the light-bridge for the timing. Initially I relied upon natural lighting for that but with night time use, added the light-bridge.
(I also have a Ninco layout in my house).
The electrics and sensors are all water-proofed and the cabling goes in to the adjacent shed which houses the power source and the connector for plugging the sensors in to a laptop computer running Race Coordinator.
The Infra-Red sensors are in sealed plastic tubes under the track glued to windows that I cut into the track surface. These have survived the life-sentence, although I had re-attach one (rusty screw!).
I mainly use it for Rally events so there is a single cross-over section to make it all one lane.
I fitted booster cables from one end to the other.
The controller connectors are the standard Carrera unit - detached from the track section and fitted underneath so it doesn't collect rain water. Again that has survived with no problem. Controllers are stored in the shed or house.
Every now and then I go round the rails with a cloth to clean off any air-pollution and bird-mess. Spider webs over the buildings are a pain but can provide "trophy dirt" for any 4x4s that run around.
Driving in the rain is a great pleasure !
The buildings are Postman Pat and Fireman Joe types as well as recognisable Scalextric stuff.
Leo