The analogue transmitters are typically five times more powerful than digital (they date back to when people did not worry about RF health effects) so broadcasting black video was a very expensive waste of electricity

Digital TV does allow more far more aggressive frequency reuse - you can see a weak co-channel signal 60dB down on an analogue TV

In the all digital world there is no good reason for Singapore to need the even number channels vacant. Expect some trading with Malaysia and Indonesia for Singapore to be able to use the 700 MHz block

Where do you live?

Taman Equine is a hilly area. Can you see Menara KL from your place?
No signal from the South as we know Seremban is a no coverage area.

It needs a second transmitter amplifier and either a combiner to a shared antenna or a second antenna

The Batang Ulu Kali transmitter should be one of the most powerful. Thanks to the height, you have clean line of sight all the way up to the hill south of Lumut

Malaysia was so late migrating to DVBT, that the video streaming sites have eaten a lot of their market

The "Free for B40s" decoders were to be paid for by the MyTV operator and a bit of subsidy from the MCM USP fund, Government never was supposed to pay. This is one reason why TM were not allowed to bid for MyTV contract in the first pace as the cost would then have been on a GLC.

TM is making a lot of money maintaining the old analog TV transmitters. There is a big hostel up in the Genting transmitter compound

Dropping the channel almost automatically raises the bitrate of all other VBR channels. MyTV has bee squeezing too much into a single Mux.
We might get some near black detail back

Adding RTM HD costs Astro serious money in transponder bandwidth. For Unifi TV, the costs are just server bandwidth. The network is there anyway.

JB zone is probably the priority to shut up Singapore

Do we know that Mux 2 (on 698MHZ) is being transimitted from all three KL area sites?
I would not expect Mux 2 to be intentionally lower power

Especially when retuning is inevitable.
When the analog tv is switched off, the MyTV network will be retuned to free up all spectrum above 700 MHz and maybe even lower for other uses.
The lowest frequencies give better coverage as a free bonus

I checked the Mux 1 and Mux 2 levels with a DVB-T SDR module and PC in spectrum analyser mode and Mux 2 looks like a different modulation option, weaker RSSI too

Today the spectrum looks similar, but Mux2 is weaker.
There are much stronger signals around 692 MHz, maybe a radio microphone. This could interfere with Mux2 reception.

After finding out that I had to use an outdoor antenna to even get a signal, I had a look at Googleearth and drew paths from my home and office to the three sites.
It turns out that my home in Ampang can only hope to see Bkt Sg Besi.
My office in Wangsa Maju is hopelessly blocked from all 3, so the signal is really weak. The reason for the strange signal on test equipment is that I am looking at reflections off buildings.
When I was planning a bid for the DVB-T several years ago, we had to plan a transmitter in North KL to get coverage in Wangsa Maju and Melawati. It looks like my planning was accurate.
Menara KL is not very useful these days, too many really tall buildings around it now.

Rain does not affect UHF very much, not like Astro Ku band. If your outdoor antenna signal vanishes in the rain, check that your coax is waterproof.

This can happen because you don't have a clean line of sight to one of the transmitters and the reflected signal will depend on the rain on buildings