I've had Clive's book for a number of years now, so I was at least aware of the Starr carbines from it (and also from "The Military Arms of Canada" mentioned below.)
I can't find any additional information in my references .... and I have looked through the index for all 40 years of The Canadian Journal of Arms Collecting. There was one article back in the 1970's by Rene Chartrand on the American breach-loaders acquired in 1866-67, but it dealt almost entirely with the Spencer and Peabody arms, with only a paragraph or two in reference to the Starr .... even less information than in Clive Law's book. There is also nothing else in the very slender "The Military Arms of Canada" attributed to The Upper Canada Historical Arms Society (six separate contributing authors) published by Museum Restoration Service in 1963.
Small wonder that little is known about the .52 caliber Starr carbines, considering how few of them there were and the fact that apparently they were never issued - at least on any "unit" basis - which is probably attributable to their requiring different cartridges than the .50 caliber Spencer and Peabody arms. As you may know, the Peabody cartridge is longer than the Spencer cartridge .... but Peabody rifles will chamber and fire the Spencer cartridge (..... not the other way round, however ....) Accordingly, the Militia Department acquired and issued only .50 Spencer rimfire cartridges, for both, thus avoiding the logistical problems which might otherwise have resulted.