Capcom could do it. Even those screenshots don't look impossible, Tuxedo Bond. Good skinning can easily negate notice of low poly models. Furthermore, coding in a progressive, distance-based level of detail would hardly be a big deal and have been used in games for over a decade now.
Besides, any game engine designed with displaying many characters on screen at once will most likely be properly coded to do so. Look at Serious Sam. That game still looks pretty good today, yet would easily run on even modest systems back when it was initially released. You could always expect to see tons of enemies at any given time, all in ridiculously wide-open areas.