Why did Pamela believe Vosen is on his way?
In The Bourne Ultimatum (2007), at 415 East 71st Street, Jason handed Pamela the confidential documents that he had stolen from Vosen's vault using Vosen fingerprint:
Jason: They'll kill you for giving me this.
Pamela: 4/15/71 isn't much of a code. My guess is Vosen is on his way already.
Jason: Why'd you do it?
Jason: Because this isn't what I signed up for, what they did to you, Blackbriar.
Actually, Pamela cleverly passes the information to Jason about his birthday, saying it was 4/15/71. The truth is that she was giving him a code, referring to 415 East 71st Street. But if Pamela doesn't think it's a secret code, then why does she believe Vosen is following them?
Best Answer
You gave the answer ("4/15/71 isn't much of a code").
IIRC, Pamela and Vosen have an argument earlier in the movie (about what to do of Julia Stiles), that's probably why Vosen decided to tap Pamela's phone.
Later, when Bourne calls Pamela, she gives him his "birthdate" (4/15/71), and says she wants to meet him and leaves the CIA building. Vosen has her followed in the hope of finding Bourne (until every agent is mobilized after Bourne broke into Vosen's office).
Then Vosen hears about the "birthdate" and immediately makes the connection with the training facility address.
Pamela says "it's not much of a code" because she knows Vosen would break it easily and would be going promptly to the meeting place.
(That, assuming Pamela knows about her phone being tapped ; not sure that information was given in the movie)
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