Here's the mid 2020s proposal from the 2011 London and SE RUS▸ executive summary:
[...]
Note that they are suggesting there that the HEx replacement by Crossrail would run on the reliefs only in the peaks. The same document also does mention in option A5 that there will be 4 fast EMUs▸ per hour running on the mains east of Reading in the peaks, covering calls at Slough, Twyford and Maidenhead.
In fact reading it again, 6 years from publication, hardly anything being proposed recently is actually new...
Paul
The Western Route Study, more recently, does take a step further in that
NR» now want those four tph for long-distance services all day, not just in the peaks. They don't mention HEx by name, but do point out its track access agreement runs out in 2023. For NR, whether they continue or are replaced by Crossrail is unimportant - just so long as they get off the Mains Lines (but of course don't fill the Relief Lines to the exclusion of goods trains).
They claim
TfL» 's support for this, though the bit they quote is really talking about these four trains going down the 'ole, not to Paddington High level.
Capability analysis identifies that eight passenger services per
hour could be accommodated on the existing Relief Line
infrastructure; subject to further assessment. Analysis provided
by Transport for London shows that there would be a positive
Generalised Journey Time (GJT) impact for passengers travelling
between points east of London Paddington and Heathrow
Airport who currently use the London Underground network to
reach London Paddington. There would be a small negative GJT
impact for those who continue to interchange at Paddington
Station with other modes, e.g. walk and taxi.
HAL have a different view (surprise!). Roughly it's that their business customers can't be expected to slum it in Crossrail's cattle trucks, they need what is in effect an all-first-class train to a taxi in central London. their supporting arguments are, of course, rather different:
• Analysis provided by Heathrow Airport Limited shows the
following potential impacts:
– Mode share – analysis shows that a combination of express
and Relief Line services provides the highest rail and overall
public transport mode share. Removal of the fast services
could increase car trips to and from the airport and related
emissions
– Passenger experience – passengers value the speed and
reliability of the current express service. Removing this will
reduce passenger experience and reduce choice for travelling
to Heathrow Airport by rail
– Resilience – a mix of services by different operators could offer
better resilience and ensures that the airport can continue to
provide public transport alternatives during times of
disruption due to incidents, maintenance or industrial action
– Economic value – Heathrow Airport is an important asset and
engine for growth generating jobs and global opportunities.
Business passengers from both the UK▸ and abroad
particularly value the express service, with two thirds of its
passengers travelling on business.
And there the argument rests, until someone (probably the minister) decides something.