Where the backhaul from one exchange goes through another, which is actually the case for thousands of them (i.e. not rare), since at the top of the pyramid there are 22 main node points i.e. where traffic from around the country is aggregated.
Then in these cases it DOES NOT affect the ADSL stats, since the backhaul is done via fibre, and if your exchange had 155Mbps of backhaul, they would have split it so that you got say 100Mbps and the small exchange 55Mbps (random numbers). This way they can manage the speed.
In short the noise margin and sync speed issues are not linked to your exchange having a satellite exchange.