You can take that a step further by running dynos in the European (eu-west-1) region: https://devcenter.heroku.com/articles/regions
It's not guaranteed. As I understand it, it's random.
And as for regions. They only help you locate content to a closer region. You cannot use them for balancing/redundancy. As any data or third party add-on you use, will manage it's data in it's own specific zone. Thus creating latency issues.
Running your own PaaS is not for the faint of heart -- and Heroku certainly saves you time and headache -- but it's nice to have a private PaaS option that is Heroku compatible.
"This post will reference the AWS services that we use behind the scenes so that we can be very specific. Note that although we will be discussing various AWS service failures, we don't blame them for what our customers experienced in any way. Heroku takes 100% of the responsibility for the downtime affecting our customers last week."
In other words, they shouldn't be exposing AWS outages to users (although as as long as they use a single cloud provider that's impossible to avoid in general.)
