Khun KJ krub, my 2 cents of thought is that the signal is totally different and they are now sending two signals, ie one analog and one digital at the same time for now as the fiber optic allow them to do both at the same time. At least, they have different contents for both signal. I think they could share the line right now as digital does not take a lot of bandwith as analog.
I'm sure they fade out analog over the next one to two years from now krub. In theory, the picture should rival that from satellite without the weather problems.