Good point. You could spin up a micro RDS instance on AWS (free for a year and much easier than installing on an EC2 instance) and it would handle this easily. I think Heroku does have a MySQL add-on, but their standard database is Postgres.
Come to think of it, you'd also need to configure S3 for file uploads (and modify osTicket accordingly) if you wanted to allow attachments, since Heroku doesn't store static files aside from those already in the code repository.
Really, at this point, given that, I'd skip Heroku and go with EC2+RDS if you're looking for a cloud-based hosting solution. Heroku is a great system and it's easy to deploy to, but it works best if the app is developed with Heroku-based deployment in mind. since there are a couple of gottchas.
