It certainly is possible to break through a phalanx from the front in EB, as proven by an old custom battle I´ve told about before. I had 3 units of Pezhetairoi, all with highest upgrades and experience versus 20 units of Red Sea Light Infantry with absolutely nothing. Oh, and I was defending a fort.
So, I put up my troops in a box formation around the gate and let them break it down, only to have my front phalanx broken within 5 seconds. 5 seconds later they´ve taken the fort square/plaza/whatever and pouring through the whole in the middle of my box.
Sure, I still won the battle, but it just goes to prove that even mediocre infantry can break through heavy experienced phalanxes from the front.