OK, this is the last from me on this, but I just found this blog post from an actual lawyer who might just know what he is talking about and it seems to support the assumptions I have been making in previous posts
“In general, an injunction made against a defendant does not affect a third party. That proposition is, however, subject to the well-known Spycatcher principle, which is that an interlocutory injunction preventing a person from disclosing private and/or confidential information also prevents third parties from disclosing the information provided they have been given notice of the injunction. The principle is based on the need to ‘hold the ring’ pending trial: if other people publish the information the claimant is seeking to protect, that will frustrate the purpose of the claimant’s proceedings. This is of course the reason why lawyers representing claimants in privacy cases normally circulate to media organisations the details of any injunction they have obtained as soon as possible after it has been made.”
So unless the lawyers contact everyone on twitter to inform them of the details of the injunction then they cannot prevent people on twitter disclosing the information. Bit of a Catch 22 really.