Putting up a trolleybus infrastructure also takes its time; you would know what impact studies have to be done before it can be done.

And, the era when the house owner got 20 francs for the inconvenience that the VBZ added an support wire hook for the wires to the house are over (that happened to a high-school buddy's parents when they did some reconfiguration with the wiring).

Crossing a complicated intersection on batteries is no serious problem anymore, considering the newest developments. In this situation, it may even be better to continue on batteries to the next stop. Automatic systems to lower and raise the trolley poles have been in existence for several decades, and would be easy to install, meaning that the driver can lower and raise the poles without leaving his workspace.

So, for trolleybuses, the implementation time is longer than for regular buses, but shorter than for light rail. However, one can consider the trolleybus an intermediate mode, and with some smart planning, parts of the light rail infrastructure is already there.