The fact that there is resistance to the eruv in Manchester just proves my point. There is a misplaced antipathy towards city eruvin. The Cabal believes that an eruv is a trick and needs to be stopped by any means available, so much so that, in their eagerness to negate city eruvin, they include non-halachic arguments, such as an eruv is likely to lead to michsholos. In fact, these secondary allegations would negate all eruvin, even private ones. It seems that these people are not troubled that an eruv is a mitzvah me’d’rabannan, and as such, they should be labeled, modern day Tzedukim or Apikorsim. Furthermore, those yungerleit who argue that halachically city eruvin are problematic are negating a mitzvah. Today’s city eruvin are an outgrowth of the halachos of shtufei mavaos which is a separate mitzvah classified in the Shulchan Aruch (O.C. 395:1). Therefore, by negating all city eruvin, at the minimum they should be labeled as eino modeh bshtufei mavaos.
Now let us explore if Manchester could even be categorized as a reshus harabbim at all.
Consequently, since each of the above conditions which are upheld by the majority of the poskim would constitute sufficient grounds to permit an eruv of tzuras hapesachim l’chatchilah, there is no reason why one could not rely on the eruv in Manchester. Moreover, since the eruv's validity rests on fundamental mitigating factors like the streets not being mefulash and the area being bounded by mechitzos, there is no doubt that under such circumstances the Mishnah Berurah ― and the overwhelming majority of poskim as well ― would agree that a Baal Nefesh could be lenient and utilize the eruv of North Manchester.
Rav Moshe Feinstein zt"l (Igros Moshe, O.C. 1:109) originally accepted as fact that shishim ribo is dependent on the street and only later (ibid., 1:139:5, 4:87-88, 5:28:5, 5:29) formulated his chiddush that in a city, shishim ribo applied to an area of twelve mil by twelve mil. According to his shita, in order for a city to be classified as a reshus harabbim, there must be 600,000 people collectively traversing the streets at the same time over a twelve mil by twelve mil area. In his final two teshuvos on the subject, he clarifies that this would require at least five times this number of people (i.e. roughly three million people) to be living in an area of twelve mil by twelve mil square (approximately sixty-four square miles). Thus, there is no doubt that Rav Moshe’s understanding of the criterion of shishim ribo is not met in North Manchester. Consequently, Rav Moshe would not classify Manchester as a reshus harabbim and would allow an eruv to be established.
The Mishnah Berurah (364:8), when describing the cities of his times, stated that there were streets that were sixteen amos wide and mefulash u'mechuvanim m'shaar l'shaar. Therefore, a Baal Nefesh should be stringent since to erect an eruv in these cities they had to rely on the fact that the street did not have shishim ribo traversing it. As we know, most towns in the Mishnah Berurah’s times were not walled ― even in earlier times most cities were not walled (Pri Megadim, Mishbetzes Zahav 362:17) ― consequently, we can deduce that he accepted the criterion of mefulash as not being dependent on a walled city.
Although some of the pirtzos may be ten amos wide, practically all poskim maintain that pirtzos esser is only a rabbinical proscription (thus, the need to close the pirtzos is only d'rabbanan, and a tzuras hapesach would suffice): Mabit in Kiryat Sefer, Shabbos Perek 16; Bais Meir, siman 364; Pri Megadim, Mishbetzos Zahav, 363:1; Shulchan Aruch HaRav, O.C. 345:11; Zera Emes, Eruvin 17; Keren Oreh, Eruvin 17b; Bais Ephraim, O.C. 26-27; Tiferes Tzvi, siman 11; Tikkun Eruvin Krakow, teshuvah 1; Melamed Leho'il, siman 68; Avnei Nezer, O.C. 265:13, 265:25, 276:1, 279:3; Aruch HaShulchan, O.C. 362:26; Mahari Slutsk, O.C. 11; Achiezer, 4:8; Chazon Ish, O.C. 107:5-8, 112:5; Chavatzeles HaSharon, O.C. 19; Kol Mevaser, 1:20:2, and Igros Moshe, O.C. 2:89-90.