Example: I live abroad but I regularly touch base with friends and family.
This could be by phone, email, letter etc, but it means that I make contact with them to assure myself that everything is OK, and to catch up news.
In your context, the writer wants to contact all the people concerned to ensure that they are all working on the project with the same goal in mind. The phrase normally is "to be on the same page".
Student or Learner