He might know how to get in touch with the underground or Cable, who could get in touch with him.
Any other Sentinels are at least 30 minutes away, for reasons that will come up, so he might have time to get away.
It might not be safe to use a prison or guard phone, but there should be a way to use a random person's phone, public internet,dead drops, etc. to send a coded message. 
That said, Corona will realize that you are gone, but will have to send a team to find you, as extracting Cable's cell is more important than one person that can survive on their own.