I'm wondering if one can change the form popup that is shown when one has a form view with a list(tree) and list is not editable. Can I define action that is called.

I don't want to change the form view from the model. Only have a different only on that list. So inheriting the form view and changing it isn't what I need.  

I think I found what I was looking for, but can someone explain me how this works. How does Odoo know to use this action

<act_window id="project_task_action_view_timesheet"
name="Timesheet Entries"
src_model="project.task"
res_model="account.analytic.line"
view_mode="tree"
view_id="hr_timesheet_line_tree"
context="{
    'search_default_task_id': [active_id],
    'default_task_id': active_id,
}"
/>