The Mu'adhin sending peace and blessings upon the Prophet after finishing the pronouncement of Adhan
After finishing the Adhan (call to Prayer), some Mu'adhins (callers to Prayer) invoke Allah's blessings upon the Prophet (peace be upon him).
Some say: "Peace and blessings be upon you, O you bright-faced, and peace and blessings be upon you light of Allah's Throne etc..." We told them that their deed is a Bid`ah (innovation in religion). They said that we hate the Prophet (peace be upon him), and that this is the norm of Sunnis and Wahhabis, i.e., followers of
Muhammad ibn `Abdul-Wahhab
who all hate Prophet Muhammad and do not like to invoke Allah's blessings upon him.
Invoking Allah's Blessings upon the Prophet (peace be upon him) is permissible, and includes a great grace. But it should be done just like the Prophet has done it at the times he used to do it. Invoking Allah's Blessings upon the Prophet (peace be upon him) following the Adhan as mentioned in the question is unlawful and Bid`ah. It involves adding to the wording of the Adhan while the Prophet (peace be upon him) said:
He who did any act for which there is no sanction from our behalf, that is to be rejected.
When the Muslim hears the Mu'adhin (caller to Prayer) making the Adhan, the Sunnah for him is to repeat what the Mu'adhin says, except when he says: "Come to Salah (Prayer), Come to success" in which case the listener should say: "La hawla wa-la quwwata illa billah (There is neither might nor power except with Allah)". After that, both the listener and the Mu'adhin should invoke Allah's Blessings upon the Prophet (peace be upon him) in the same manner which the Prophet (peace be upon him) mentioned including the following manners:
O, Allah! Send prayers upon Muhammad and the family of Muhammad, (Part No. 5; Page No. 75) just like You sent prayers upon Ibrahim and upon the family of Ibrahim. You are indeed the Praiseworthy and the Glorious. O Allah! Bless Muhammad and the family of Muhammad, just like You blessed Ibrahim and the family of Ibrahim. You are indeed the Praiseworthy and the Glorious.
Also it is sufficient for the person to invoke Allah's blessings upon the Prophet in the shortened form, i.e. "Allahumma Salli Wa Sallim `Ala Rasulallah" (O Allah send your peace and blessings upon Allah's Messenger) instead of the innovated forms mentioned in the question. Then the person should say:
O Allah! Lord of this perfect call (of not ascribing partners to You) and of the regular prayer which is going to be established! Kindly give Muhammad the right of intercession and superiority and send him (on the Day of Judgment) to the best and the highest place in Paradise which You promised him.
As for doing so in the microphone collectively, it is a Bid`ah and impermissible.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.