Publicize G _ What type of post is made?

Publicize creates link posts, with an excerpt of your post and an image if your post includes one. Here is an example:
https://plus.google.com/+JeremyHerve/posts/c73Tb4Qzxn8

Can it be configured to post the meta description of the post in place of the excerpt?

I’m afraid you can’t customize the text used there at the moment, but I took note of your suggestion and we’ll consider adding that option in a future Jetpack update!