The Minchas Yitzchak (2:132) brings the Magen Avraham in Orach Chayim 90:17 and 235:2 with an understanding that not only isn't it considered תפילה בציבור but it is not even considered בשעה שהציבור מתפללין, which would be of a lesser power but the tefillah is heard.
The Minchas Yitzchak also brings the Tzlach (Berachos 6a) who understands the Magen Avraham to only say that if a person davens a different tefillah than the tzibbur while not being in the synagogue together with them, only then is it not considered to be בשעה שהציבור מתפללין and that the tefillah is not heard, but were the person to daven with the Tzibbur in the same place then the Tefillah would be heard. The Minchas Yitzchok maintains that even according to the Tzlach it is still not on a level of בשעה שהציבור מתפללין, but nevertheless the tefillah has merit.
The Mishna Berura in 90:30 writes, based on the Tzlach, as follows :"ואם מתפלל עמהם בביה"כ מיקרי תפילת הצבור" which the Minchas Yitzchak points out, sounds like it is real tefillah betzibur and contradicts the Minchas Yitzchok's understanding in the Tzlach and Magen Avraham.
Others (Ishay Yisroel 8:14 footnote 38) also interpret the mishna berura to not mean that it is real tefillah betzibur.