With Google Takeout, there's an option to "Transfer your Google+ connections to another account," which means your circles, blocks, and other connections are transferred.
However, your Posts, About Me information, photos, videos, +1s, and other information is not transferred:
When the transfer is complete, your circles, blocks, and ignores are copied from the source account to the destination account. Circles in the destination account with the same names are merged. Content from your source account (such as profile information, posts, or comments) is not transferred to the destination account. Similarly, authorship information and Google+ pages that you manage with your source account will not be transferred to the destination account. However, this content, pages, and authorship information still exist in your source account.
Seeing as it's incredibly easy to import and export blog posts (e.g. Blogger), I feel like it wouldn't be too hard to transfer this information from one Google+ account to another.
As of now I've transferred my circles over, but I'm still looking for a way to migrate my Stream (a.k.a. posts), photos, and +1s. This article (Lifehacker.com) is very misleading because while it is technically not incorrect, it leads the reader to believe that this data is easily migrated. In the beginning it mentions that migrating all of the data is easy, but after the steps for migrating Circles, it doesn't mention how to migrate any of the other data. The last paragraph briefly touches on migrating +1s, but does not go into detail:
Your +1s can also be imported into most web browsers as bookmarks. If you're using Chrome, Google will be able to sync them.
I've also used Takeout to download an archive of my Stream, photos, +1s, etc. onto my hard drive, however there is no easy way to import them into my new Google+ account. Of course, I could re-post my posts, re-upload my photos, and re-+1 my +1s, however the timestamps and URLs would all be changed and the previous comments would all be gone.
The bottom line: Is there an easy way to transfer post data and other history from one Google+ account to another?
Best Answer
The bottom line is, no, there is not.
Unlike Blogger, which has a way to write posts externally, Google+ does not have any such public system, and Google appears to have not wanted to support such a thing to migrate posts at this time.
Make sure you use the Send feedback system to make sure they are aware of your displeasure with this situation and urge them to completely implement the migration feature.