So they’re finally reusing and repurposing something rather than just building new.

As to what they know, much of military intelligence is educated guesswork.
This is an easy solution.
Be it terrorists, a Carrington event or a simple mistake, in many respects this is the cheap insurance policy and will probably save much of the Springs economy.

As to the ancient tech, the problem is the gear is hardly compatible with modern gear and nothing works together, hardware or software.

Even 80’s gear is ancient and uses programming that few today can understand. Especially the modern generations. Go back to the 60’s and 70’s and the old legacy units and we may as well be talking about alien technology.