So I misread the specification originally: NIST and SECG actually make no reference to encryption/decryption or signing/verification in their specification:
"NIST Recommended Elliptic Curves for Government Use" http://csrc.nist.gov/groups/ST/toolkit/documents/dss/NISTReCur.pdf
"SEC 2: Recommended Elliptic Curve Domain Parameters"http://www.secg.org/collateral/sec2_final.pdf
(secp256k1 defined here)
They simply recommend elliptic curves and provide the associated parameters needed for implementation. These curves can be used with any EC-based algorithms, including ECDSA and ECIES.