My first approach was to open a case on Cisco Meraki Support. But the reply was "Unfortunately, this is not something that support can provide. You should be able to get this information from your account manager (help -> Get help)".
Since it was urgent (just needed that to close the answer to an RFP) I have used the MTBF indicated by MerakiDave.
It seems either something changed or you got a support person that didn't know they could provide them. I have for sure in the past got these numbers from support.