Just for interest, I looked it up and that's not exactly what Section 155 says:
http://www.bclaws.ca/civix/document/LOC ... section156
Your reference to "extra caution" is about the Sec 155 Subsection 2 exemption for crossing the line to avoid an obstruction in the road. However another car traveling at the proper speed limit is not an "obstruction", so you wouldn't be entitled to the exemption through Sec 155 Sub 2.
Sadly I do think there is at least some basis for your objection, however small and unjust it may be:
Sec 155 Sub (1) (c) one single line, broken or solid, the driver of a vehicle must drive the vehicle to the right of the line, except only when passing an overtaken vehicle.
Your situation sounds similar to this discussion:
http://drivesmartbc.ca/lanes/double-sol ... mment-1199
But suppose we consider your argument that you applied "extra caution". A justice has to determine if that is a credible statement. A sworn officer will state that you certainly didn't apply extra caution, and will be supported by notes indicating you were observed and/or clocked at 90 km/hr. Any sober justice will hear that and will have serious doubts about your claim of using "extra caution".
The rules seem to create a contradictory situation. The road you were traveling sounds maybe rural or whatever with a single solid line. An exemption to crossing that line exists for people entering and leaving their driveways. The town can't just make it double solid, because that would affect the people living along it who will want the option of turning left or right as they leave their driveways.
So what remains is the issue of were you safe to cross over a solid line into oncoming traffic direction? It then becomes a subjective call, open to law enforcement discretion. I suspect that if you were traveling 50 and crossed over to pass a horse carriage going 20, the officer would have made a different subjective decision than he did watching you blast down the road at 90 km/hr. Agree?
To recap for simplification:
Your defense is you crossed over the center line to overtake a vehicle. Did you do this safely? No, because you were speeding.