Culture is observable in small behaviors. Whether a meeting starts with the number or with the opinion. Whether an analyst can say the data does not support the plan without a career cost. Whether a report that shows a failure gets circulated or gets revised. Whether people go looking for existing data before commissioning new. None of that comes from a poster; all of it comes from what senior people are seen to do when the data is inconvenient.
In practice. Culture moves when the incentives move. The most effective single intervention is a leader publicly changing a decision because of evidence, and saying that is why. That is worth more than a year of communications.
Where it goes wrong. Culture is treated as the program's soft, unmeasurable component and handed to communications. It is neither soft nor unmeasurable: count how often the numbers in a decision paper are reconciled beforehand, how many decisions cite a source, how long it takes to answer "where did this come from". Those move, and they can be tracked.