It is absolutely welcome. Most of the PacificNG staff are CP/UP fans, understanding the standard gauge system out west is vital to understanding the narrow gauges themselves. If it hadn't been for games played by the CP and SP, many of the narrow gauge lines in California wouldn't have been built. The South Pacific Coast Railroad was built to compete with the CP, and won. There is plenty of overlap between the SG and NG practices, don't forget most of those narrow gauges had to connect with something for transshipment.
Not only that, the CP/SP and UP both had controlling interests in many narrow gauge railroads. The Utah and Northern (which is not yet on the site) was controlled by UP starting in the 1880s and they applied the same standards to the narrow gauge equipment as the standard gauge. The CP/SP did the same operating lines in Northern and Southern California before they gained control of the C&C. After 1885 the SPC is controlled by the SP and they repaint everything to SP standards, right down to the passenger cars.
I actually model the V&T circa 1900 in HO scale (narrow gauge stuff I build in On3 for display), so the CP/UP and others go right along with my interests. Daniel and Curtis know this first hand, they've seen PacificNG members in action at the V&T (and SPNGHS) conferences. Most importantly, PacificNG isn't supposed to be just a couple people, everyone is encouraged to be involved.
PacificNG was created to consolidate information, this includes "honorary" narrow gauges like the V&T, Sierra, Colorado Midland, etc. It is meant to be a place to ask questions and discuss various topics. There is plenty of room for fictitious railroading too! John Ott, Don Ball and many other "Early Rail" enthusiasts use PacificNG on a regular basis. Our forum is a little slow since I broke the style template last year, but you're absolutely welcome to post about your projects fictitious or otherwise in the forum. Variety is the spice of life.
About the only thing that would be frowned upon would be post-1924 D&RGW, there are plenty of other places to look for that information.