ISA's behind the times,...the UK has had the Certificate of Competence in Mobile Elevated Work Platforms (MEWP) for years already.
You get to take the assessment and have your cert endorsed on the specific type of equipment that you use all the time. The assessment is verbal and practical, NO multiple choice questions! Can you operate it and do you have sufficient underpinning knowledge to prove you understand the basic ins and outs of your equipment. Risk assessment and safety features are an integral part of it all.
There is also a cert. in the use of a chainsaw from a MEWP as well.
If you want to compare check out the assessment criteria at
http://www.nptc.org.uk/assessment-schedules/
Under plant machinery is MEWP assessment and under chainsaw and related operations is chainsaw use from a MEWP.
The assessors have to have a minimum of 5 years experience, hold the qualification themselves, undergo a technical evaluation by a verifier who is even more experienced, then do a course in assessment technique, and be observed carrying out two assessments BEFORE being accepted as an assessor. Then every two years assessors must be verified by being observed carrying out an assesment to ensure they are still applying the correct standards and assessment technique. They also have to attend periodic standard setting and technical update events to stay current.