Assurances have been made to passengers that rail services will be improved as a result.
The work is set to allow for the use of more electric Great Western Railway (GWR) services and also help launch the Elizabeth line between Reading and Heathrow across London.
This Christmas marked the biggest single Network Rail engineering operation for Crossrail, with major works being completed in London, Berkshire and Essex.
More than 4,000 workers carried out 330,000 hours of work over 10 days during the festive period.
Programme director for Crossrail at Network Rail, Matthew Steele, said: “Successful completion of these Christmas works was vital to delivering the Elizabeth line.
“As part of our Railway Upgrade Plan they will benefit passengers by improving reliability, increasing the capacity of the rail network and enabling the introduction of new rolling stock that has more seats and offers faster journeys.
“I would like to thank passengers and our lineside neighbours for their patience whilst we carried out our work over the festive period.”
The improvements made over Christmas include the opening of a second ramp of the Stockley Flyover at Heathrow junction and a new diveunder at Acton.
These will be used by GWR and Heathrow Express trains, and will add capacity and improve reliability on the busy section of rail.
GWR managing director, Mark Hopwood, said: “We started to run our first new electric trains in September and with this Christmas work completed, on time, I am delighted to say that we can now deliver even more of those improvements – with half hourly services between London Paddington and Hayes and Harlington.
“The new trains will deliver consistent, high quality travel for customers across the Thames Valley, offering at-seat power sockets, air conditioning, extra luggage space and free WiFi for customers."
There was no service in or out of Paddington main line station between December 24 to 29 while work was carried out.
A reduced timetable was also also in place between December 30 and January 2, and between Christmas Eve and December 29 there were no trains between Paddington and Ealing Broadway.
Crossrail is a new railway for London and the south east, running from Reading and Heathrow through 42km of tunnels under London to Shenfield in Essex and Abbey Wood in south east London.
The £14.8billion project began in 2009 and is due to be completed in 2018 with the official opening of the Elizabeth line.
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