I think your SPAs do "IP over E3/T3":

http://www.cisco.com/c/en/us/products/collateral/interfaces-modules/shared-port-adapters-spa-interface-processors/product_data_sheet0900aecd8027ca19.html

For the other way around (circuit emulation - "E3/T3 over IP") you would need something like this:

http://www.cisco.com/c/en/us/products/collateral/interfaces-modules/shared-port-adapters-spa-interface-processors/prod_data_sheet0900aecd8073c18b.html