Brake line failure in '95 Caddy STS

Recently while travelling on the 401 HWY in Toronto, Canada at approx. 100KM my brakes completely failed when coming to a rather quick stop....the pedal went to the floor on the second pump of the pedal....any further pumping resulted in no braking action and NO pedal pressure I was lucky enough to bring the car to a slow and meger stop using the emergency brake! I am surprised that this Caddy does not have a dual braking system...if it does why did it fail completely?
Once the car was towed to my mechanics he said the brake lines were badly rusted in spots and a section just forward of the fuel filter location on the drivers side let go...hence loosing all the brake fluid.
Can someone tell me if rusty brake lines in a 1995 Caddy STS with 150km on the clock is a common occurance...this car has rarely been winter driven and has been oiled sprayed!
Also, does this car have a dual braking system and if it does why did it fail?
Your help and expertise is greatly appreciated.
Ron J. Zeraldo 

How many lines are rusted thru? Most newer cars have diagonal brake system. Meaning lf and rr and rf and lr brakes are tied together. Total brake failure is rare. Unfortunately most of Canada and a large part of the US fall under the "RUST BELT" and rust is a major issue with vehicles operated in the salt enviroment even on a limited basis.

Thanks for your reply note...one section so far shows were the line burst resulting in a loss of fluid. When under the car and examining the lines most from the master that run down the firewall seem to be bad, then there are sections that look like new, then those that run over the rear axle housing are showing extreme rust! To me this looks very unusal...I own a collection of old british sports cars and even they don't show this type of rust after 30 -50 years of driving. Do you know for certain that the '95 caddy sts has a dual braking system?
 
Regards,
Ron    

Car was designed for US, US DOT has required dual brake systems since 1968.

....FYI, I just got my caddy back, replaced all of the brake lines, an $800 bill plus taxes!!! I would recommend to all caddy owners a thorough inspection of the hydraulic brake lines once the vehicle is 5 years or older...especially if you live in the RUST BELT!
Ron