Sky has its own propriety EPG system and all tuning data it needs will be included within or alongside it on the same transponder.
For other satellites, it does not need an EPG, just a list of the frequencies on that satellite and a decoder needs to able to access these to scan for all channels - which you then select or put into favourites. No need for an EPG.
In the case of ASTRA2 it would appear that transponder 11222 has this info because if you set network search OFF it finds just a few channels from a single frequency. Put network search ON and it scans all the frequencies transmitted by the satellite. The same ought to hold true for other satellites. Is this true? If it is, how come the thousands of satellite websites don't mention this.
I have a HUMAX TN5000HD and the rather illogical user manual says that network search OFF scans for 'transponders by default from the factory'. This of course is not true.
In the case of SKY, it seems to have a single transponder with the info you suggest but why can't they say so?
Also in the HUMAX manual they continue to bang on about Symbol Rate which is completely irrelevant. Comms systems automatically synchronise to the symbol rate and it is not as though there are different channels on the same transponder frequency depending on the symbol rate. I really get the impression that the inventors of all this are technically incompetent.
However, I have found my channels but am no closer to a proper explanation about how the transponder protocols work or the structure of the transponder information database :-(