klark0 - 3:59 am on Nov 6, 2012 (gmt 0)
It is not actually public. Try accessing your own https://plus.google.com/XXXXXXXXXXXXXXXXXXX/plusones when logged out
In my case, it redirects to https://plus.google.com/XXXXXXXXXXXXXXXXXXX/posts (the page where my public updates are visible)
And on other people's profiles I can't even see that tab.
There might be an option somewhere to make it public but I don't see one...
I guess we can use ole Matt as an example.
https://plus.google.com/+MattCutts/plusones [ [plus.google.com...] ]
That URL seems to be indexed, and it can be viewed whether logged in or out at G+.