I’ve used the GE and the Siemens UPS systems in the past, both at complex hamburger junctions as back up to give time for temporary traffic management to be deployed. From an operational point of view they both worked the same, both had a good series of operation outputs that could be picked up by remote monitoring and both switched over seamlessly from mains to battery power.
The GE system did requires a pretty large cabinet, the link below should show you its the two door cabinet. Not all the space inside was used for the batteries but the space was needed to keep air flow around the system. The Siemens system fitted nicely into a standard 900 cabinet and from that point of view had a much smaller visual impact.
From my experience getting the remote monitoring is important as if you don’t know its on batteries its not much point. Along with the standard fault bits I think we went for ‘on battery’ and ‘1hr battery’ left. That way we could tell the TM crew to get ready and then to deploy the TM before just before signals went off.