I checked and found Roger Whittaker's web-site. There's a guestbook, and I asked about the recordings it's on, and the author(s). Here's what I got back
Anthony D.P. Mann
Wed Dec 28 23:37:26 2005
Hi! In response to Mr. Seto, "Canada Is" was written by Steve Hyde & Eric Robertson, and exists in several versions. The song is available on the wonderful LP "Travelling With RW", and is available on CD on the Tembo release of "Greatest Hits" (TMCD4331). A live version of the song also appears on the "Live in Vienna" LP ("From the People, To the People" in Canada). Roger performed this song during the 2004 Greatest Hits tour - a very special song for our very special country.
Vicky and Rory
Wed Dec 28 23:52:49 2005
This is further regarding "CANADA IS". In addition to the information provided by Anthony Mann, "Canada Is" is also available on RCA Canada KCD1-0118, the CD reissue of the 1975 Greatest Hits LP, KPL1-0118. These are the short 3'20" versions. The longer 4'30" version seems to only be on RCA Australia and Philips Norway LPs and cassettes.
For those who care about these things.