Lots of missing information, mis-information and outright BS posted here..
" Three days later the brakes seized up."
What does THAT mean?? Contaminated fluid usually makes the brakes turn to mush, the pedal dropping to the floor..
The ONLY way to determine if the fluid has actually been contaminated would be to send it out to an oil analysis lab. So far, everything posted here is just guess-work and opinions.
If you want to play games, take two small glass jars and pour an ounce or two of brake fluid in each of them. Then add an ounce or two of motor oil in one and power steering fluid in the other and shake them up. Observe the result. Do they mix and stay mixed? do they separate? If they separate, which fluid goes to the top and which to the bottom? Then go to a parts store and buy one wheel cylinder kit for any drum brake application. Drop a rubber cup into each jar. examine the cups every day and report back if/when they swell up and get all distorted and soft..
Then we can debate some FACTS instead of someones opinion and guesswork..