I am trying it now, can it be done?
Yes, it is possible to import notes and associate them to the exchisting tickets.
The steps to import notes using Import2 Wizard are pretty easy:
Upload your CSV file, select “notes” as the type of data to import.
Map the fields you want on the note itself (i.e. body/description of the note, timestamp) and the links to the records you want to associate the note to (i.e. ticket).
Here is a video overview on how to import notes into Hubspot and link it to excisting records: