This case was a reference to the Advocate General by the Belgian National Courts. The Court was asked for guidance on whether 'working time' per Directive 2003/88/EC includes situations where workers are required, on a rota basis, to be on stand-by within a specified radius of their workplace.

The worker, a firefighter in this case, was required under his terms of engagement to be available and on call for work one week in every four, including evenings and weekends. During these stand-by periods he had to remain contactable and, when required, report to the fire station within eight minutes. In practice, this meant the worker must reside near the station and his activities were restricted when he was on call. However, he was only paid for time on active service and not for being on call.

The Advocate General held that the definition of working time should not automatically be extended to include workers on stand-by duty who are required to quickly respond to their employer's calls and whose activities during this period are limited. Instead they indicated that the overriding factor to be considered is the quality of time the worker can enjoy when on stand-by, rather than the degree of proximity to the work place required. Accordingly, they held that the classification of on call time as 'working time' should be based on the individual facts in a case and the quality of time the worker enjoys whilst on call.
http://curia.europa.eu/juris/document/document.jsf?text=&docid=193236&pageIndex=0&doclang=EN&mode=req&dir=&occ=first&part=1&cid=790918