A Prison Service source suggested the prison van ambush would probably involve one of the escapees having access to a smuggled mobile phone.
A phone call could then be made or a text sent to let the armed gang know which prison van they were in and so which vehicle to target, among the number of vans making their way from jail to Manchester Crown Court.
More top news
Rescue workers are at the site Sunday morning trying to cut open mangled coaches.
Despite chilly temperatures it will be a mostly dry day, and milder than yesterday.
The Sunday Times alleges a missile malfunctioned after launch during a routine test of the UK's nuclear deterrent last year.