N.Y. Comp. Codes R. & Regs. tit. 16, § 684.5 – Radio-telephone utility plant accounts.

(a) All radio-telephone utility plant shall be recorded at original cost. Except that original cost of plant acquired from another utility or radio-telephone utility prior to the date a utility becomes subject to this system of accounts may be estimated, if not known. Adjustments to reflect such estimated cost shall be made in accordance with the text of account 102, Radio-telephone Plant Acquisition Adjustments.
(b) Each company shall establish a list of property units having the following characteristics:
1. (1) Groupings or property units should conform with the plant accounts prescribed in this system of accounts.
2. (2) Property units should be suitable for retirement purposes and should be neither so large as to cause most replacements to be charged to maintenance, nor so small and numerous as to make accounting and recordkeeping burdensome.
  Note:
  See List A [List A is set out at the end of the system of accounts for Classes 1 and 2, infra.] for suggested list of property units.