The Marque guidelines are very straightforward - they just codify normal best practice in cellarmanship. Each candidate is surveyed twice in three months and after the award follow-up visits are made to ensure consistency. However there are problems with one aspect. It is recommended that cellar coolers are set at 54°F and that beer is served at a maximum of 60°F. This certainly aids consistency and may be appropriate in the height of summer but many people find that this results in unpleasantly chill beer at other times (e.g. as sometimes found in The Hogshead). Failure to meet these temperatures is the most common reason for failing to pass a survey.
Pete for one is well aware of this and will adjust settings accordingly. He reports that they've now revised the limit to 61°F (which surprisingly makes a significant difference).
Scottish Courage have decided to trial Cask Marque in Bristol, leaving Bass as the only big brewer ignoring the scheme.