Your friend is correct. As the codex says, "All models benefit from the appropriate Chapter Tactics for their detachment's Chapter, providing they have the Chapter Tactics special rule" (emphasis added). Unless the vehicle has Chapter Tactics (and none do), they can't benefit from the Raven Guard chapter tactics.
For further confirmation, consider the Iron Hands' Machine Empathy special rule: "All vehicles and characters in this detachment have the It Will Not Die special rule (even though vehicles do not have the Chapter Tactics special rule)" (emphasis added). If Raven Guard vehicles were supposed to have Scout, they would have had a similar exception.