Yes you can import new accounts in bulk AND generate usernames and passwors automatically.
What I would do is create a few accounts using your provisioning form manually. Maybe 5 accounts will do the trick. Then export these accounts to a .csv file.
Use the CSV as a template and and populate the columns for as many accounts as you need. You can leave the usernames blank.
Then got to import the accounts. Browse to the saved .csv file or if it is small enough copy and paste it into the import box. After you click next you will be on step 2 of 3. There is a box at the bottom called Match Fields. In the username drop down you have the option to set it to a random username. Below that is the option to use a random password.
I did this once for 20,000 accounts on an Aper system. Exported from Aper matched columns to CPPM (AmigoPod at the time) and did the import. Its important to have a template first using a form you created especially if you want emails to be sent to the users after the accounts are created. Make sure you have SNMP working and the settings tested in the form before you make your template.
Also I suggest you set the accounts to force a password change on first login. Hope this helps.