It will apply to lanes on east and west Belfast routes and 12-hour bus lanes in the city centre, which link them.
The trial relates to Class A taxis and any of the remaining taxis still licensed as private hire and public hire outside Belfast.
However, the trial, that begins on Monday, has come under criticism.
Sustrans, the sustainable transport charity, said it was disappointed by the move which it said was "a potential setback for cycling in the city".
It said it believed the decision was premature "as there are currently limited alternatives for cyclists given the lack of a segregated bike network in the city".
Sustrans added that in "the absence of segregated cycle lanes, bus and cycle lanes (their official title) have become safe havens for cyclists".
The trial includes bus lanes on the following routes:
The Department for Infrastructure has said its aim is to "balance and respect the needs of all road users".
It said it would assess the impact of the taxis on the operation of the bus lanes during the trial period.
"This will include the safety of bus lane users, as well as the impact on journey times, vehicle speeds and volumes," it added.
"The department will also invite stakeholders to provide their views before reaching a decision on the long term access arrangements for taxis in bus lanes."
Class B and Class D taxis are already permitted to use all bus lanes in Belfast.
Class C taxis (intended for specialist services such as weddings and funerals) have not been permitted access.
Further information on the 12-week bus lane trial is available via the Department for Infrastructure website.
A 12-week trial scheme for some taxis to use bus lanes on Belfast Rapid Transit (BRT) routes has been announced by the Department for Infrastructure.