I had the same problem, only I wanted to show fields only to users in a group. I solved this by inheriting the view and made changes to the specific group.

In your case it should look something like this:

<?xml version="1.0"?>
<openerp>
    <data>
<record model="ir.ui.view"  id="view_id">
    <field name="name">view.id</field>
    <field name="model">your.model</field>
    <field name="inherit_id" ref="id_of_inherited_view"/>
    <field name="groups_id" eval="[(6, 0, [ref('base.group_userA') ])]"/>
    <field name="arch" type="xml">
        <field name="WO_NOTES" position="attributes">
            <attribute name="readonly">1</attribute>
        </field>
    </field>
</record>
    </data>
</openerp>

Hope this helps!