It hasn't been mentioned for a while but Millportpoloco is and has always been a no gears event ( fixed/free* we're not fussy ) purely because at the time of the first Millportpoloco there were no Glasgow couriers not riding track bikes. You're more than welcome to come with a geared bike, there's no snobbery here, but you will not be eligible for any prizes.
*I think the only person to ever turn up on a singlespeed was 13yr old Lewis on his BMX