As per the title really, if I can upload my public key into AAISPs systems, then when emailing billing/usage etc those communications can be sent for my eyes only.
At the same time AAISP could sign the communications using their key.
Would seem to me to be a not entirely difficult to implement an additional lookup to see if there is a public key on file as the email is generated, and if so encrypt.....
Being optional (only if I've uploaded a key) - this wouldn't negatively impact those who aren't interested or able to set up such.
Allowing for entirely routine communications to be encrypted by default is a excellent way to stand up for personal privacy rights.
It could also be argued that at least in principle, as AAISP uses another telco's infrastructure to deliver service, and AAISP are also in competition with said other ISP then communicating in the clear over their infrastructure regarding AAISPs ongoing contracts with subscribers is less than ideal.