By default, all administrators of one business account can see support tickets created by different admins. Open My Tickets page and see ticket creator in Author column:
Add ticket watchers
To share ticket with other members of business account, either license administrators or regular members, open ticket details by clicking on ticket subject > switch to 'Ticket Watchers' tab:
Then select a person in the dropdown and click Add:
Once added, the person will receive an email notifications about ticket updates and will be able to view this ticket in his Parallels account's My Tickets page.
Remove ticket watchers
To remove ticket watcher, click on cross button and next to corresponding account: