Yes I have done this.
You just setup a subdomain CNAME and make sure your IT guys have it as alias to any existing email boxes you want to monitor. The details would vary by server type.
for instance, you could have
email@example.com be the primary box, but firstname.lastname@example.org would be a valid alias.
You would then have to setup Marketo to have spf/dkim for that subdomain.
Then you can use the @news.company.com emails in your marketo emails. There's not a real setup to do once your IT guy handles it.
As for sender reputation, there are good docs on ramping up an IP address, but in all honestly, this isn't necessary for a subdomain. You should probably mention the minor change in an email and ask folks to add the new address to their contact lists. In my experience, this step wasn't necessary and we had no impact on our deliverability.
I do see this practice and generally recommend it in these situations.