While formally there's no precedence, court decisions still influence jurisprudence (I.e. the interpretation of the law), especially when supreme courts are involved.

From the Wikipedia article on Civil Law:

In actual practice, an increasing degree of precedent is creeping into civil law jurisprudence, and is generally seen in many nations' highest courts.[11] While the typical French-speaking supreme court decision is short, concise and devoid of explanation or justification, in Germanic Europe, the supreme courts can and do tend to write more verbose opinions, supported by legal reasoning.[11] A line of similar case decisions, while not precedent per se, constitute jurisprudence constante.

The last sentence also explains why Sony tried to do this in Germany: they were hoping to have a book sized legal thesis they could shop around in other European courts.