Administrative Regulations for Number Portability Services of Telecommunications Enterprises Article 28

When an operator leases or lends subscribers’ numbers for other operators to provide telecommunication services, it shall not restrict other selection service providers from providing Number Portability, and shall negotiate with other operators on items specified in Articles 5, Article 7, and Article 27.
中文原文 電信事業號碼可攜服務管理辦法第28條
經營者出租、出借用戶號碼供他經營者提供電信服務時,不得限制他經營者提供號碼可攜服務,並應與其協商第五條、第七條及第二十七條所定事項。

English translation for reference only; the Chinese text prevails. Not legal advice.