Wolverine is shown on the last page of Hulk #180, but the third page of Hulk #180 has a Canadian military boss telling the team to react to Hulk by "mobilize Weapon X". So, Wolverine is "activated" in the story on the third page, and is "on his way" (behind the scenes) until he catches up to Hulk and Wendigo on the last page. He didn't just come out of nowhere with "Hi, I'm Wolverine, there's no reason for me to be here - tune in next month..."