Update to earlier post:
So after 2 days of internet outage and spending those days on re-configuring my home network along-with 40-emails long exchange (configuration-focussed, not moaning) with TES engineering team, both STBs and the internet are working fine now. However, I've had to be taken off bridge mode for this to work.
It appears that once you go with IPTV you can't have brdige mode on ONT. At least this has been my experience with Transworld so no idea if other ISPs can do this. To their credit they did try to make this work in bridge mode. I even asked them if somehow the ONT could be in half-bridge mode (e.g. port 4 on ONT for internet bridge and rest of the ports for STBs) or if there are some IPTV specific settings that I could do in my router but the engineering guy called me and said that this would not be possible. So important lessons learnt:
1. Try not to resolve technical issues in evenings on public holidays. I did the mistake of replying to their email that STBs weren't working at 7:00 PM on 1st day of Eid, I don't know what configuration they tried to do but the internet didn't work from 8:00 PM onwards. I had to reply to their emails via phone and suffer 2 days of outage before things were back to normal. From now on I would only try to resolve technical issues in mornings on working days.
2. The STBs should be connected directly with ONT or with switch directly connected to ONT. One of my STB was connected with a switch which was not directly connected with ONT but connected with a WAP in-between. Occasionally there was some stuttering on this STB and some channels didn't work at all. Once I connected this switch directly with ONT, the problems went away.
I would say their customer service response was not bad given the circumstances. The IPTV service runs great, channels switch fast and there's no "buffering" at all. It works like normal cable. Maybe other IPTVs are like this too but this is my first experience with this and it looks great to me. baller23 earlier posted the picture gallery for the STB and channel list here if anyone wants to have a look:
http://imgur.com/a/qcpvA69