The EU Clinical Trial Regulation 536/2014 has been made final and was published in the Official Journal on 27 May 2014. It does define start of a clinical trial.

A2 (25) "‘Start of the clinical trial’: the first act of recruitment of a potential subject for a specific clinical trial, unless defined differently in the protocol";
HOWEVER --- “Whereas: (38) The date of the first act of recruitment of a potential subject is the date on which the first act of the recruitment strategy described in the protocol was performed, e. g. the date of a contact with a potential subject or the date of the publication of an advertisement for a particular clinical trial”.
Article 36 requires the reporting of both the start of CT (as in Article 2) and FSFV (First Subject First Visit) in each MS within 15 days! So lots of fast reporting to be done. There will be a need for a fast and reliable reporting system by sposors.
Annex 1 Application dossier for the initial application K. RECRUITMENT ARRANGEMENTS(INFORMATION PER MS CONCERNED) 59. “Unless described in the protocol, a separate document shall describe in detail the procedures for inclusion of subjects and shall provide a clear indication of what the first act of recruitment is".
So it is up to you to define things sensibly in the protocol or a separate document. There is advice (& webcast) on this sort of thing on the RQA website (www.theRQA.com).