I'm pretty sure that you can gather this from vrealize operations using the VRA management pack.
I have a weird work around.
You can use the IaaS API but, you will get information about existing VMs (not deleted vms). And, you cannot filter the query using a custom property value.
So, if you can narrow the search using dates (maybe VMs created last week) this could help you:
Method: GET (with NTLM authentication)
Headers: Accept: application/json
IsManaged eq true -> means only managed by vRA (you can imagine other filters using the attributes of the response)
expand=VirtualMachineProperties -> retrieve custom properties
You can browse the response, every VM will have all Custom Properties and you can find one with name "__clonefrom". The value will be the name of the template.
Hope this helps.
Thanks for the tips. We may try out vRealize Operations soon, but for now the IaaS API seems promising for this. I found an example vRO action that I am playing with now to see if it will work:
It would be nice to also get data on past deleted VMs.