Praise be to Allah.
If the imam always recites the last verses of Soorat al-Baqarah in Taraweeh or in Shafa’ and Witr because he believes that it is Sunnah, this is a mistake. What is proven from the Prophet (peace and blessings of Allaah be upon him) is that he used to recite al-A’la and al-Kaafiroon and al-Ikhlaas. It was narrated from Abu Dawood (1423), al-Nasaa’i (1736) and Ibn Maajah (1171 – this version was narrated by him – that Ubayy ibn Ka’b (may Allaah be pleased with him) said: The Messenger of Allaah (peace and blessings of Allaah be upon him) used to pray Witr and recite Sabbih ismi Rabbika al-A’la (al-A’la 87), Qul yaa ayyhu’l-kaafiroon (al-Kaafiroon 109) and Qul Huwa Allaahu ahad (al-Ikhlaas 112).
Classed as saheeh by al-Albaani in Saheeh al-Nasaa’i.
Whoever wants to follow the Prophet (peace and blessings of Allaah be upon him), this is his Sunnah. There is nothing wrong with reciting other passages of the Qur'aan, but one should not persist in reciting a specific passage and never reciting anything else, for that may come under the heading of reprehensible innovation (bid’ah), because he is singling out a specific passage for this prayer that the Messenger (peace and blessings of Allaah be upon him) did not single out, and seeking to draw close to Allaah by means of something that He has not prescribed, which is bid’ah (innovation).
And Allaah knows best.