Manchester Airport does not recognise premium class travellers, nor elite status FFP’s. It is upto the airlines agents to provide the means to you to access the fast lane. As you may have experienced theres little green MAG stickers for fast lane access. The airport charges the airlines per passenger a premium and they count this by stickers issued.
The queues are MAG’s fault and as such they will not want to be liable for delays to passengers (IATA 85 or 87) so anyone with a short departure time may have been permitted access to the fast lane. If you’ve checked in online, a short dash to your airlines ticket desk or premium checkin the staff should give you a sticker for your boarding card. For mobile boarding cards I cannot comment though.
I’ve had a few flights cut fine recently where even crew are delayed due to Manchester security.