If that was the case, two different connection methods would make sense, not using Ethernet x2 which is what's happening here. Being able to daisy-chain cameras seems more likely.
Don't think so. Having two different networks in a building is pretty common, but I haven't seen any in-building net not using Ethernet in the past 20 years. Fiber is still being terminated and turned to Ethernet usually.
Not saying it wouldn't be better - but I don't think that's what people would usually do.
Not saying it wouldn't be better - but I don't think that's what people would usually do.