Can I install Warmrails in a shower enclosure or above a bath?
Warmrails are designed to be splash proof. They are not designed for immersion in water, being drenched in water or in fact anything more than the occasional splash. If there is a chance that the Warmrail could encounter more water than the occasional splash it should not be mounted in that location. A showerhead in the bath will definitely cause a lot of splashing.
Your Warmrail should be wired into a circuit that is protected by a GFI (circuit breaker). This is important, however most power sockets in modern bathrooms should already be GFI protected as a standard. If you are still unsure you should refer to your local city building code for guidelines.