And Oswald's transfer was planned and announced at a certain time, but it didn't happen. It was delayed. The last delay caused by Oswald himself. Nobody could have anticipated that.
Yet the evidence is that Ruby had just walked in seconds before Oswald came out the door. If Ruby had been relying on even inside information, he would have been there much earlier. It simply wasn't possible to have been pre-planned.
Actually, there are news reporters who witnessed Ruby waiting about the building on the outside that day.
Please note first paragraph if this link works: Ruby lurked and waited for Oswald.
There is much more, I think Ruby actually talked with a news worker in the street that day in regards to when Oswald was being transferred or something like that. I read it some time ago but the info is out there.