Yes, you can do a VPN between a ASA 5505 and a UC520. However, you must use crypto maps for any VPN between a IOS-based endpoint and a non-IOS-based endpoint. Since the UC520 is considered a IOS-based endpoint and the ASA 5505 is a non-IOS-based endpoint, you must use a crypto map to configure the VPN between the ASA 5505 and the UC520. Remember that the UC520 can only handle 10 VPN connections.

An example of a VPN between an ASA and a IOS-based router is shown here:

http://www.cisco.com/en/US/products/ps5855/products_configuration_example09186a0080a9a7a3.shtml

Remember that the UC520 side of this VPN must be configured in CLI, as SDM cannot be used on the UC520, and CCA does not have the ability to provision a site-to-site VPN (except to other UC500 sites managed by the Multisite Manager). However, you can use ASDM to configure the VPN on the ASA side.