How can I override a typesafe config list value on the command line?

An alternative syntax is implemented in version 1.0.1 for this:

-Dpoller.datacenters.0=SJC -Dpoller.datacenters.1=IAD

I had the same issue some weeks ago, and finally dived into the source code to understand what's going on:

• This feature is not implemented, it's not possible to define a list using command line argument

Fixing it wouldn't be that hard, but someone need to take time to do it.