The prosecutor can't literally use what you say during the resolution meeting against you. Discussions between counsel for the purpose of out-of-court resolution of an existing matter is priveleged and cannot be used in court.
The worst case scenario for you is that he prosecutor will know what you will say, and might prepare for it (i.e., you lose the element of surprise). But that means the prosecutor will take note of it for his collegues, since there is no guarantee of who will prosecute that case once it gets to trial. Also the prosecutor may be prompted to seek any additional evidence ahead of time to refute your defence.
Generally speaking, crown prosecutor are weary of using what you say at the resolution meeting to prepare their case, because there is no guarantee that this will be your defence once the case comes to trial, and if you change the defence, then the rug will be swept from under the feet. Unlike appeals where your factum will detail out your case that they get to respond to (or reply to depends on what the case might be).
Having said that, you know that City prosecutor that handle traffic matters aren't counsel most of the time, therefore they may still do the opposite of what a decent lawyer for the crown would do.