There are several different sets of instructions for installing the Mobility stuff, none of them complete. Here's what I've worked out needs to be in the PRO file:
For the includes to work, you must have done the install/config per the instructions in the Symbian bin distribution, so that the epoc include directories get updated appropriately, and, to use the <QClassName> includes, you must have done the configure sequence on the Mobility directory that is described elsewhere.
CONFIG += mobility
MOBILITY += systeminfo bearer (whatever subcomponents you use)
INCLUDEPATH += <Qt install path>/qt-mobility-src-1.0.0-beta1/include \
LIBS += -lQtBearer \
symbian:TARGET.CAPABILITY = NetworkServices (or whatever -- most functions are going to use some)