I submitted a T562 for an client who has control over her deceased son’s estate (intestate). I filed the doc via Submit Docs with a letter and a copy of the form attached, although a bit in the reverse order of yours (no difference, really, than filing a DC and a Will). Thread is below:
Deceased client, T562 filed, how best to file AuthRep? - protaxcommunity.com
It took CRA a while to process, but it eventually showed up on RAC.
Suspect a similar approach here will work. BTW - there was NO communication from CRA at all, it just showed up.