(idiomatic, intransitive) To fit in or harmonize (with something).
This paragraph does not tie in with the greater themes of the story.
"It works out perfectly for us," said Phoenix during an interview with CBC News that was at times interrupted by the sound of drills and saws. "It ties in nicely for our opening and it's just a good way to create a buzz with a new business." 2019 March 8, Andrew Lupton, “JUNOS value to London? Try $12 million to start”, in CBC News, archived from the original on 15 Sep 2021:
For a local station to begin broadcasting an ongoing network transmission.
I believe Argentina has a network of about 20 or 25 stations that they can tie in. 1938, United States. Congress. Senate. Committee on Interstate Commerce, Construction and Operation of a Radio-Broadcasting Station (page 105)