In the recent discussions here about why TfL was planning to sell and lease
back an existing fleet, in order to finance the new Piccadilly line fleet,
we all assumed it was one of the LU Underground fleets. This made little
sense, to me at least, as bespoke Tube trains are of no value to anyone but
LU (and the Island Line), and would therefore not attract leasing
companies. The deal would consequently be expensive for TfL.

I commented that ROSCOs were much more interested in standard products that
had other potential users, such as Electrostars and Aventras. Well, it
seems, I'd accidentally almost stumbled on what's actually happening: TfL
is planning to sell and lease back the fleet of class 345 Crossrail
Aventras that are currently being delivered. That makes much more sense, as
it's better to own the unique, highly customised new Piccadilly 4LM fleet,
and to lease the fairly standard Aventras, than vice versa:

https://www.londonreconnections.com/2018/leasing-lizzie-finding-the-funds-for-deep-tube/

The story also confirms that the overdue Piccadilly order should be
announced imminently.