What do you mean by summary? If you want to see the user activities like, active users, how frequently a user is using the model, how many logins did he make in a model etc.. then you can go for a Splunk Report. Drop an email to support.anaplan.com asking for Splunk Report they should be able to give a brief summary of User access.
Sounds like what you are looking for is Tenant Admin. You have to be set up for this but it will allow you to go to tenant admin and then you can see by user, which models they have access to. Someone at your company will have tenant admin and be able to add you as a tenant admin as well. If you are the owner of Anaplan at your company, you can work with your Business Partner and Support to have you enabled for tenant admin as well.