Q. When davening amidah together with the shliach tzibur, word by word, as when you arrive late and can’t do it with the minyan. When the shliach tzibur says birchas Cohanim (Elokeinu V’Elokey Avosenu), should you say with him word by word too or just keep silent?

A. Aruch Hashulchan (O.H. 109: 11) debates whether it should be recited or not. He mentions that it cannot be compared to reciting anenu on a day of fasting, that Maharil and Matte Moshe rule not to say with the shaliach tzibur, because anenu is a brocho by itself. However in regards to birchas Cohanim his opinion is that it could be said. (Shevet Halevy (6: 13) rules that one reciting word by word with the shaliach tzibur should avoid saying the tefilah for dreams at that time, even if needed, since it would be considered a hefsek.)

Horav Shlomo Miller’s Shlit”a opinion in regards to birchas Cohanim is similar and it could be recited together with the shaliach tzibur word by word. He also pointed out that some maintain that Elokeinu V’Elokey Avosenu is recited by an individual in his silent amida (Tur O.H. 127)

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a