802.3ad/LACP between Administrative Domains

We have a GE link to another SP and bridge a single VLAN ID to connect multiple hosts on each side. We'd like to increase the BW between the two networks, but the other provider cannot support upgrading to 10GE. What are the issues w/ running 802.3ad LACP between two separately managed networks and binding Nx1GE links:

- Does this require BPDU forwarding across the links, and share a common STP for the VLAN? We currently filter BPDU's across the single link.

- Any known LACP negotiation issues between a Cisco (6500) and Foundry (unkn)?

- Is there the potential for layer 2 loops if LACP fails and BPDU's are being filtered across the links?

- Bad experiences w/ 802.3ad when loosing one of the two links?

Thank you for your input.