SpamCop.net blacklistings are typically temporary (12-24 hours) and usually due to a message being flagged as spam (the most common reason). This normally doesn't cause much of an issue as a range of IP's are used to send out emails, so one single IP being blacklisted for 12-24 hours isn't a huge concern.
The Marketo Deliverability Team takes all blacklist listings seriously and will actively work to resolve them as soon as they are aware of them.
Should you notice severely reduced deliverability rates on emails or receive a notification that emails you've sent out via Marketo are blacklisted, please let Marketo Support know as quickly as possible.
Have a great day!
Jesse