I think it's easy for someone to call themselves bilingual. Take, for example, a judge who is doing some shopping over at the Rideau Centre; they might consider themselves bilingual if they are able to converse with the sales clerk or someone else and have that person understand them.
Where the distinction comes in is in the courtroom. If the judge doesn't have the language proficiency to be able to communicate in both official languages with the party in question or to make a quick, reasoned and consistent determination after hearing the evidence at a bail hearing, that judge is not bilingual. In that case, we are talking about the judge's language proficiency.