It is a response to the argument that the Traditional Mass exemplifies 'clericalism', because it doesn't have swarms of lay people in the sanctuary, reading the lessons, cleansing the sacred vessels, leading prayers and hymns and distributing communion.
Dr Shaw says "The key point of the paper is that, while at least some 'special' lay roles in the liturgy are perfectly defensible - serving and singing being the obvious examples - even these don't exist for the sake of the liturgical participation of the people doing them. This is a crucial point. Without it the rest of the congregation may well feel excluded wrongly from graces available only to the parish elite."
The paper (number 29) can be read here.
All papers (1-29) can be read here.