Do you know if this document is used anywhere besides Canada?
I don't have copies from any sources other than from Canada, but the document is in widespread use inside and outside Canada based on what is published in medical literature on the subject. For instance, Nationwide Children's Hospital in Columbus, Ohio has developed a training seminar for clinicians that heavily admonishes use of the document in pediatric JW cases.
Also, in the 2005 incident of the 14-year-old Canadian JW who left Canada for treatment at Schneider Children's Hospital in New York the agreement reached between the US medical facility and the JW girl's family (with Watchtower's support!!!) was the same as found in the Letter of Understanding document. My opinion is that the horribly bad press Watchtower was suffering at the time in cases like this compelled it to relax its 1992 position, which allowed for this agreement that was later framed as a form document for institutional use. But to the day Watchtower has not once advertised this agreement (or the form) among JWs for use by parents and their children. This lack is one reason for my blog article on the subject. Advertise! Advertise! Advertise!