this is also the time of shit like "metropolice force" / MPF or hell, even
OTA which we still use; from what we can tell from other Nova Prospekt lines, the TA (
not OTA) is more akin to a 'sub-branch' (albeit a very dominant one at the time of hl2) of something called the 'Stabilization Force' (which falls well under lines like 'stabilization delegate', 'stabilization team', etc.) which is what the soldiers are derived out of
makes a lot more sense in early occupation when you think about it. any army guy fresh off the resonance cascade would want to do their part in 'stabilizing' the planet. the transhuman arm would come later as an add-on and doesn't necessarily replace that organization
my interpretation is simply that SF is the name of the organization and nova prospekt is simply the particular branch of it. so there's a city 17 stabilization force, city 14 stabilization force, etc.