Yes. The USMCA entry for land surveyors lists a baccalaureate degree or a state, provincial or federal licence as alternative credentials, so a valid Ontario licence satisfies the qualification without a degree. Citizenship, prearranged professional work and the absence of U.S. self-employment still have to be shown.
The licence is the credential; the letter must match it
The land-surveyor entry is one of the few where a licence stands on equal footing with a degree, and officers apply it as written. The surveyor should present the physical licence, a standing letter dated within the last few months and government identification showing Canadian citizenship. Where cases go wrong is the description of the work: if the U.S. firm's letter calls him a field coordinator or a survey technician, the officer may reasonably ask whether the work is professional surveying at all. The letter should say that he will conduct and certify boundary and right-of-way surveys, that this is the work of a licensed land surveyor, and that the engagement is expected to last a stated period. Nothing in the entry requires U.S. licensure for admission; that is a separate professional-practice matter in the state where the fieldwork occurs.
Hypothetical example: a licensed cadastral surveyor is offered a six-month assignment to verify easement boundaries for a U.S. utility contractor. At the first review, compare the licence number and standing record with the precise services in the scope. The decisive record is the signed engagement letter: it should call for professional survey work, identify the U.S. client, state who accepts the deliverables and give an end date. If the scope instead assigns only data collection under another professional's supervision, the parties must explain why the listed profession is still the real role. Sequence the licence check before travel planning, then obtain state practice advice for the work location. A current Ontario credential answers the TN qualification issue; it does not itself authorize a signature or seal required by a particular state.