Okla. Admin. Code § 730:40-5-2
The following words and terms used in this Chapter shall have the following meaning, unless the context clearly indicates otherwise:
"Class II and Class III railroad" means a railroad that is classified by the United States Surface Transportation Board as a Class II or Class III railroad;
"Eligible taxpayer" means any Class II or Class III railroad; and
"Qualified railroad reconstruction or replacement expenditures" mean expenditures for:
(A) reconstruction or replacement of railroad infrastructure including track roadbed, bridges industrial leads and track-related structures owned or leased by a Class II or Class III railroads as of January 1, 2006 or
(B) new construction of industrial leads, switches, spurs and sidings and extensions of existing sidings by Class II or Class III railroad.
Okla. Admin. Code § 730:40-5-2