This is one of the few places where reading a standard literally gives the wrong answer, because the operative text predates a later rule that the standard itself points to.
The requirement. A body belt shall be worn and a lanyard attached to the boom or basket when working from an aerial lift (29 CFR 1926.453(b)(2)(v)). Attachment is to the boom or basket, not to an adjacent structure, because the point of the rule is to keep the worker in the basket during a jolt or catapult event.
The note that changes it. The note to paragraph (b)(2)(v) states that as of January 1, 1998, Subpart M (29 CFR 1926.502(d)) provides that body belts are not acceptable as part of a personal fall arrest system, and that use of a body belt in a tethering system or a restraint system is acceptable and regulated under 29 CFR 1926.502(e). So the paragraph now reads as: tie off, and if the system could arrest a fall, wear a full-body harness.
Restraint versus arrest. A restraint system is rigged so the worker cannot reach a fall hazard; an arrest system catches a fall in progress. In a basket, a short lanyard that keeps the worker's feet on the platform floor is restraint, and a belt is permitted. A lanyard long enough to allow a worker to be thrown clear of the basket is arrest territory, and only a harness will do.
Other aerial lift duties. Employees must stand firmly on the floor of the basket and may not sit or climb on the edge or use planks or ladders for a work position (29 CFR 1926.453(b)(2)(iv)), manufacturer's boom and basket load limits may not be exceeded (29 CFR 1926.453(b)(2)(vi)), and lift controls are tested each day before use (29 CFR 1926.453(b)(2)(i)).