Sorry rancher, I can't answer this question. However, I would think any country which imported boat loads of infectious meat and bone meal from the UK would be on the look out for BSE. They would want to be able to sue the UK government, just as France reportedly is, for causing their BSE problem and harming their industry.
I understand what you are thinking, if they don't test they won't find it; however, the UK diagnosed BSE on Guernsey Island by clinical symptoms only:
OIE chart, UK BSE cases:
In Guernsey BSE is generally confirmed on the basis of clinical signs only. To date, a total of 600 animals have been confirmed without laboratory examination.
This shows that a country need not rely on lab tests for diagnosis. Of course (in my opinion), you'd have to be a blooming idiot not to test animals suspected of having the disease. But the UK has shown us that they relied upon visual inspection only on Guernsey Island, so why couldn't these other countries do the same.
Being the world is a small place, now of days, I don't think you could hide the disease for very long. Though some might be better at that then others.