David E. Belcher wrote:

Does this include the necessary tweaks to the track and signalling
arrangements to allow Silverlink to run through to Euston from St.
Albans Abbey?

Almost certainly not.

Anyway, are through Euston to St.Albans Abbey trains really better than
a through Watford Junction - St.Albans City light rail service?

--
Aidan Stanger
http://www.bettercrossrail.co.uk