Those suggesting, or objecting to, any particular privatisation ought to have a read through it for a handle on the base theory on this stuff. Whether privatisation is best depends a lot on which model you think applies.
From Walker's conclusion
...there is an implicit assumption in the literature discussed above that economic efficiency is a major objective of privatisation but the, ex ante, conditions sometimes imposed by governments on the sale of assets often serve political rather than economic ends. Examples of such conditions are things like the New Zealand government’s restrictions on foreign ownership and the desire to sell to ‘Mums and Dads’, both of which restrict the number of possible bidders. Such conditions also result in fragmented ownership, making it difficult for owners to coordinate their efforts to effect the firm’s behaviour. In addition, given that each ‘Mum or Dad’ will own only a very small share of any of the firms, they have little incentive to become informed on the firm’s activities since they will only capture a very small amount of any improvement in performance they could bring about. These factors suggest that, in practice, little will change in terms of the behaviour of the SOEs: they will remain, for all intents and purposes, government-controlled entities. This contradicts the very reason for privatising SOEs in the first place.