Hi Shaun,
It is currently possible just not documented as it should be.
The templates live under /Data/MessageTemplates
and you can specify it to use custom templates from config settings
<add key="EventCalProCustomConfirmationSubjectTemplate" value="CustomEventCalProCustomConfirmationSubjectTemplate.config" />
<add key="EventCalProCustomConfirmationBodyTemplate" value="CustomEventCalProCustomConfirmationBodyTemplate.config" />
<add key="EventCalProCustomAnonymousConfirmationBodyTemplate" value="CustomEventCalProCustomAnonymousConfirmationBodyTemplate.config" />
this would require you to create the files on disk on the MessageTemplates folder, the actual files need a prefix like en-US-CustomEventCalProCustomConfirmationSubjectTemplate.config
you would want to base them on the default files
en-US-DefaultTicketOrderConfirmationPlainTextEmailTemplate.config
en-US-DefaultTicketOrderAnonymousConfirmationPlainTextEmailTemplate.config
en-US-DefaultOrderConfirmationEmailSubjectTemplate.config
Best,
Joe