Hello Pedro,
they are completely independent as explained by Jon.
It is a "ships in the nigh" approach.
The two ospf processes can be in competition in providing a route for a given prefix and as explained by Laurent the decision taken from the IP routing table mantainer is not based on OSPF route type but only on timing.
To handle this kind of scenario with multiple OSPF processes and some level of prefix overlapping you can use the distance ospf command under router ospf to differentiate AD for internal, inter-Area and external routes
distance ospf {external dist1 | inter-area dist2 | intra-area dist3}
Also OSPF default routes are affected by this kind of competition between processes.
see
http://www.cisco.com/en/US/docs/ios/iproute/command/reference/irp_osp1.html#wp1013195
Hope to help
Giuseppe
