Hi there,
Can I clarify if you mean for all systems with reseller access to in ASUP, or do you mean for ALL customers?
The script linked does it by subnet scanning and then logging into each controller - so you would need to have IP and account access to them all. There is "Get-NcMetrocluster" cmdlet which might be of assistance.
If you're looking from it from the point of view of a reseller, I don't think there's an easy option from autosupport.
If you are internal to NetApp, and are looking for ALL customers, I would suggest emailing John K who does our install base analytics - if you don't know him, please send me a PM with your netapp.com email address and I'll put you in touch.