Meanwhile I was doing some research and found out as a fellow canadian I benefit from canadian laws which unless I'm mistaken is 50 years after the composers death, according to my research, (but just noticed you had posted this) as for US and UK it's 70 years. This actually gives a HUGE advantage as a musician, in my current project I need to use some Rachmaninoff, this means no publisher's permission needed, how sweet it is. [:D]
Guy, there are different rules for different countries. I think that Australia is another 50 year territory, yet I also seem to remember that Spain and Belgium are (or at least used to be) 83 year territories. Rachmaninoff would seem to be out of Copyright in Canada, but check very carefully about the years added on due to the World Wars, if any. There is also a possibility that an editor has made changes to the scores that you are looking at. One would think that this would come under the heading of corrections, but in some cases Publishers claim that a new Copyright has been created. What is worse, is that in some of these cases the original manuscripts are kept under lock and key, so you can't even find out what the changes are!
The fact that you live in Canada is only an advantage if your music, or arrangements are only ever broadcast in Canada. As soon as they go to a territory that has different rules, you are in breach of Copyright, and the TV company would have to negotiate with the Publishers for that region to be allowed to use your arrangement.
Copyright rules can be a nightmare, and it is worth the cost of legal advice to make sure that you don't breach them.
DG