It would be interesting to know what professional (as opposed to political) advice they had on this, because if they are complaining about higher costs of a trolleybus system, then they're going to be in for an unpleasant surprise with the costs of a battery bus system. They have plenty of European partners to advise them on this and I'm surprised at the outcome. The clue might be the reference to the aesthetics of the OHW, which makes it a political matter and one has to ask how strongly was the case for an IMC system with a reduction in the amount of OHW put forward?
The case for modern IMC trolleybus systems is pretty-well summarised here:
(The information on the Prague system is outdated as the city is replacing its entire diesel bus system with IMC trolleybuses, not just the airport route.)
The pattern that's evolving in Europe is that battery buses are being used on less busy routes, while the major, very busy routes are serviced by trams, trolleybuses and/or metro. Battery buses in Europe typically have quite a low range and rely on frequent top-up charging in order to avoid increased weight due to batteries and thus to be able to carry more passengers. Top-up charging also involves downtime, which is something detrimental to a busy system.
Tony P