That is a contract question, not a legal one: the government's admission fee or I-129 filing fee is set on the USCIS fee schedule, but who pays it, and who pays for translations and advice, is whatever the offer says. Ask before accepting.
Put the cost allocation in the offer, not in an email
Government charges for TN are modest at the port of entry and larger for a Form I-129 petition, especially with premium processing, and current figures live on USCIS Form G-1055 rather than in any adviser's quote. The bigger question for a Shannon applicant is allocation. U.S.
employers are not obliged to pay TN costs the way they are for some other categories, so the offer letter should state whether the company covers the filing fee, legal fees for the support letter, translation of Québec credentials and relocation. Hypothetical example: a Colorado software company offers a systems analyst a relocation allowance but says nothing about immigration; she should ask for a clause before signing, including who pays if a request for evidence follows. Costs for a spouse and children in TD status are separate lines and almost always the applicant's.
A quoted professional fee should say whether it includes advice on the ownership or venue questions or only the letter itself.