I don't know what POOR'S is, so I don't know why or how the data would have been collected for this publication.
By 1909 the WP&YR had purchased all the locomotives it would use until 1938 when the first 2-8-2 #70 was purchased. Therefore by 1909 it could have rostered 19 locomotives, #s 51 to 69, not including the 0-6-0 Duchess and the 3 truck Climax #8 [which was used only for the construction of the railway and was sold in 1902]. Of those 19, #s 55, 57 and 63 were sold to the KMRy in 1902 and # 65 was sold in 1906. Therefore in 1909 it's unlikely that the WP&YR could have owned more than 15 locomotives. Thus I would see the tabulated data as duplications for purposes of Canadian vs American accounting only and therefore the greater of the two tabulations for locomotives and rolling stock is probably the most accurate. It would be interesting to see how the tabluation would compare for 1910, 1920, 1930 and 1940.