NEC ECC: Deemed acceptance of quote?

NEC 3 Contract. Clause 62.4 states the Employer has 2 weeks to reply to a quotation submitted by the Contractor. If the Employer does not reply within 2 weeks is it assumed the Employer has accepted the quotation?

No - first the Contractor has to notify that there has been no response to the quotation (62.6). After a further two weeks of no response (to the reminder) only then would it ever lead to a deemed acceptance in terms of time/cost.