Sidewalk Labs reportedly lists its city plans in a "secret" coffee table book that it has on site to inspire employees, which are encouraged by higher ups to read through the book to obtain that inspiration. The book is said to contain everything from potential planning operations to innovative ideas on how to solve problems that cities may be facing in regards to urban planning, though it's worth noting that it was hailed as a book that was designed to provide a look to recruits and current employees at what the vision of Sidewalk Labs is, so it's not really a book that contains actual plans the company has in the works.
That said, it's reported that the book may have alluded to possible future sites for smart cities beyond the city of Toronto, Canada, which could include the cities of Alameda, Denver, and Detroit among a couple of others. These cities were described as having some or most of the key components needed to make them ideal cities for the sort of projects and improvements that Sidewalk Labs was created for which includes but isn't limited to large areas of empty and unused land that's more centralized in a part of the city which houses lots of businesses.
Whether or not Alphabet's Sidewalk Labs will expand beyond Toronto, which itself is still in an unfinished state as far as the project goes, is unclear, but it seems like the company has an active imagination and would like to be able to move forward with resolving urban planning issues in other cities besides Toronto. The book though, serves as a way that the company as a whole might come up with ways to turn the company's vision into a reality in places where it has yet to start any projects, filled with interviews with urban planning experts in addition to ideas on how to solve future problems, and studies of other cities which have actually solved urban planning issues.