Originally Posted by
Singlecoil
The source of the altimeter information comes from either a human or automated weather observation for that airport. The facility you reference is the controlling ATC for that airport, kind of an apples and oranges comparison.
SoCal controls BUR, LAX, VNY, SNA, etc. If an altimeter is missing for any of those airports and they happen to give you one from another field, that doesn't necessarily mean you are legal to shoot the approach.
I'm not quite sure if you are saying that you can not use an altimeter setting from another field in order to shoot an approach to a different field with your above bolded statement; but if you are, here is an example from a small field that I was using this past weekend.
http://204.108.4.16/d-tpp/1101/00022IL31.PDF
Now if you are talking about SoCal specifically then I assume that there would be some airports where the same would be true, though the airports in the LA basin might not have an example.
USMCFLYR