Not really. UMTS typically runs around 2GHz (in some countries lower bands are also used, list here), and 1,8GHz is also used for GSM for example. Besides, for steel-reinforced concrete, 2GHz often goes through while 900Mhz (typical first generation GSM) does not. You should also realise that a large part of the propagation goes via reflections (e.g. on walls), in some cases streets act as waveguides. Propagation in these frequency bands and in cities is relatively complex.

As far as the air interface is concerned, the main characteristic of UMTS is that it uses spread spectrum on a 5 MHz wide channel. This is mainly what makes it different from GSM which uses TDMA on 200 KHz wide channels. UMTS degrades more softly when propagation is bad or when more users are added to a given cell.