It's evolving but for now, it's promoted on SC.
If Wayne is game for doing so, he could add a blurb ""Upcoming Webinars"" to the monthly (weekly?) newsletter and to the website. The trick there is that it might get in front of non-90 Minds Members (customers, other partners, Sage people, unknowns). I don't have a problem with it necessarily but broadening the audience will (should?) impact the webinar focus.
Platinum and Gold Vendor Members are entitled to have an ad on the 90 Minds site but I just checked the site and it's not clear how that is getting fulfilled. And ... again ... the website is open to all comers so promoting the webinar on the site through their ad may change the audience. I don't have a problem with it but we should discuss what it means for vendor members and regular members attending.
If 90 Minds is promoting customer-facing webinars, we need to be clear about it with the members. Personally, I think it would be a good thing provided the vendor members are aware of the associated partner so nothing unpleasant happens.