The original bus station at Westbourne Park had to be demolished to free land for the project and a temporary site is presently in use.
The works in Contract 336 will require the construction of a new bus deck extension next to the railway capable of parking 150 buses.
It is estimated to come with a price tag of £25m to £50m and will also include final track formation works at the site.
The replacement bus deck project is programmed to start at the end of 2013 following the completion of the Crossrail tunnelling works and will run for around two years.
Interested firms have until 20 September to submit PQQs through the Crossrail procurement portal.