What happens to 20CN ADSL when exchange upgraded for FTTC ?

[#1]

When 20CN telephone exchanges are upgraded to facilitate FTTC,  does the "up to 8Mbps" ADSL stay as it was,
or does it ALWAYS get upgraded to 21CN ADSL2(+) ?

[#2]

I might be wrong here, but I think some exchanges have had FTTC before being upgraded to 21CN. I believe they piggy back to another local exchange with 21CN.
I think this is quite rare though, and normally the exchange will become 21CN enabled within a matter of months.
In terms of product upgrades when the exchange is 21CN enabled, I think this still has to be manually done. But it's in the interest of the ISP (cheaper) and end user (potential faster speed) to be moved over ASAP to 21CN. Some of the 20CN products are being retired soon for new customers - I'm not quite sure what ends up happening in rural or non-cost effective areas where 21CN/fibre have been slated.

[#3]

20CN Datastream (not used by many ISPs) is being withdrawn everywhere I believe.
20CN IPstream (ADSL1) is being withdrawn from all exchanges which have 21CN available. Going by an exchange I know about, it appears the 20CN IPStream stop sale date is a year after 21CN is enabled, with the withdrawal up to a year later.