JC:
That terrain I see on Google Earth rising to 844 feet asl is offset 5 degrees from the final approach course (measured from the center of the theshold).
The VGSI criteria are not part of the FAA's instrument procedures design criteria. They are contained in an FAA Airport Division's 1500 series advisory circular. I recalled from memory a 15 degree splay for the VGSI. That was an incorrect recollection. It is 10 degrees. I don't have the criteria at hand but the 10 degrees is from a 2004 article on the subject I wrote for Business and Commercial Aviation. I had the VGSI criteria in hand at that time.
If, and I emphasize if, the PAPI at hand were designed correctly, the Birmingham airport authority would have had a competent survey team survey all obstacles out to 4 miles to assure the 3.2 degree PAPI surface had not less than 1 degree of obstacle clearance.
Apparently the NTSB is now very interested in verifying such a survey.
In any cases my work involves assessing the IMC phase of instrument procedures, not VGSIs. The FAA has a big computer in OKC where the design work (prior to flight inspection) is done at a desk. As good as the obstacle data are, they are insufficient to design the final approach segment of approaches with vertical guidance "APVs (ILS, LPV, LNAV/VNAV, and RNP AR). On site surveys are usually required for APVs.
I have no doubt all the special RNP AR IAPs that exist in Canada today were most, if not all, subject to a rigorous survey for the final segment.
Sometime in the 1990s I wrote an article for IFR Refresher article, "What's Below DH or MDA." The FAA stance was worse then with respect to NPAs with straight-in MDAs than it is today. You can ferret out that article at
www.terps.com if you care to.