flectra/addons/account_asset/security/account_asset_security.xml

<?xml version="1.0" encoding="utf-8"?>
<flectra>
    <data noupdate="1">
        <record id="account_asset_category_multi_company_rule" model="ir.rule">
            <field name="name">Account Asset Category multi-company</field>
            <field ref="model_account_asset_category" name="model_id"/>
            <field eval="True" name="global"/>
            <field name="domain_force">['|',('company_id','=',False),('company_id','child_of',[user.company_id.id])]</field>
        </record>

        <record id="account_asset_asset_multi_company_rule" model="ir.rule">
            <field name="name">Account Asset multi-company</field>
            <field ref="model_account_asset_asset" name="model_id"/>
            <field eval="True" name="global"/>
            <field name="domain_force">['|',('company_id','=',False),('company_id','child_of',[user.company_id.id])]</field>
        </record>

    </data>
</flectra>