Understanding client event and overriding tree_but_open

Hello folks,

I'm trying to understand how the client event binding works.
To sum it up briefly, I would like to override this in product_view.xml of product base module:
(line 277)
        <record id="product_normal_action_tree" model="ir.actions.act_window">
            <field name="name">Products</field>
            <field name="type">ir.actions.act_window</field>
            <field name="res_model">product.product</field>
            <field name="view_type">form</field>
            <field name="view_mode">tree,form</field>
            <field name="domain">[('categ_id','child_of',[active_id])]</field>
            <field name="context">{'categ_id':active_id}</field>
        </record>
        <record id="ir_product_category_open" model="ir.values">
            <field eval="'tree_but_open'" name="key2"/>
            <field eval="'product.category'" name="model"/>
            <field name="name">Products by Categories</field>
            <field eval="'ir.actions.act_window,%d'%product_normal_action_tree" name="value"/>
            <field eval="True" name="object"/>
        </record>

What I would like to achieve especially is to be able to override those 2 fields in one of my module:
            <field name="domain">[('categ_id','child_of',[active_id])]</field>
            <field name="context">{'categ_id':active_id}</field>

I've tried to apply my modification directly in the core files and it works as expected, but now I would like to do it the clean way.

If someone can help me understand how to either override or redeclare this and how to bind it to the right action, I'd me more than pleased ;-)

Thx,
John