That is relatively easily to accomplish. It would be a 2 part process in order to restrict per project and to restrict per users.
Log into site admin and click on the Licenses tab. That will default to Status view and show you your license names (type) and expiration date, in use and max count, etc.
Should see Business Components listed as a type for your 10 BPT licenses .
Click on the License Assignments tab.
This will show you a Domain list and under it project lists. Click the project you want those 10 BPT to go to.
On the left is the project name, and on right are columns like Full License, Performance Center, and Business Components.
For the row entries for a project, you can for the Business Components column enter value of 10 so that then all your BPT are for this one project. Only that one project then will have use of the BPT licenses.
Click Save once you have your value/s entered.
Log into the project where you assigned the BPT licenses via ALM client and enter the project customization.
You will then want to create a new user group for this project. Use tdadmin as base and remove down permissions. TdAdmin is always advisable to be the source for new custom groups. Little more work but the less future issues make it worthwhile. Remove everything not needed for these users per module.
Once done, add your 10 users to this group. Make sure these users, and all users, are in one group only.
Next, after you get your permissions set for this new BPT group, you must remove the BPT access on the other existing groups. Go to Module Access and remove the Components column (module) check box for each group besides your newly created group. This will help to prevent even project admins from consuming the license. And if needed, under groups and permissions, you can alter the permissions for the Business Process Testing features. This likely won't be needed if you remove module access, but keep in mind the features are there if you need to limit your newly crafted BPT user group.
Save everything and exit customization. At this point your BPT group should be the only users who will have access to the Business Components and thus consume a license.