I just noticed that a full score was posted. Grofe, whose orchestration was uploaded, died in 1972. As I understand it, this means the score in question is likely not PD in Canada until Jan. 1, 2023. Unless Canadian law treats "derivative works" as mere adjuncts of the principal work, in which case Grofe's orchestration has no independent copyright status from that of the original version.
The other factor potentially arguing against the validity of the 1942 copyright would be if a set of parts and/or condensed score were issued earlier. All full score is merely a compilation of the parts and would enjoy no copyrightability separate from the parts. In practice, full scores were typically issued long before parts, but not always. That doctrine comes from US law anyway, so a separate publication of parts and/or condensed score might have zero bearing under the Canadian statute.
Sorry to act like "the enforcer" around here, but we are being watched very closely. It's important to be up front and transparent about this issue.
BTW, Gershwin and Ravel's works (along with those of other composers who died in 1937) do not become public domain in the EU until Jan. 1, 2008.