UK Rail Replacement Bus delay - can you still claim Delay Repay?

Revised answer after further research.

London TravelWatch is the independent, statutory watchdog for transport users in and around London. In these consumer affairs committee meeting notes we can read the following:
2.4 To check the legal position for passengers

The Director, Public Liaison reports that the ticketing contract entitles you to travel between the starting point and destination. It does not specify whether the service is a railway service or a replacement bus but the operator should advise you in advance if it is a bus if possible.

2.6 The rights of passengers in event of breach of conditions of service

“Passengers on rail replacement services are entitled to the same conditions as these travelling on normal rail services. Therefore they are entitled to delay repay in the event of delay. The EU Regulations on rail passengers rights and obligations if enacted, will strengthen the rights of passengers to be provided with assistance and refreshments in the event of delay and full refunds in the event of severe delays leading to cancelled trips.“

The National Rail Conditions of Carriage state:

60. Carriage by road vehicles

These Conditions apply to passengers travelling and luggage, articles, animals and cycles conveyed in road vehicles provided by a Train Company or its agents unless it is made clear to you when you buy your ticket that different conditions apply. The term “train” in this context includes any road vehicle owned or operated by a Train Company or on its behalf.

Individiual conditions of carriage may override the above and a page with pointers to the individual train operating company's CoC can be found here. Some parliamentary comment can be noted on the lack of standardisation:

There is also a complete lack of standardisation. The only common element of Delay Repay schemes across the train operating companies is the 30-minute threshold for compensation—everything else differs. The circumstances in which compensation can be paid vary; some compensation schemes include the weather and planned engineering works, whereas others exclude them, so there is no clarity about what passengers will get.

Although there is a typical exclusion in the various CoCs stated as:

Delay Repay is a national scheme train companies use to compensate passengers for delays. You can claim compensation if you're delayed by more than 30 minutes when you travel with us (except when delays are caused by planned engineering work).

This appears to be related to delays relating to the original scheduled time when the timetable has been amended due to delays, e.g. from the UK Citizens advice bureau comment on engineering works :

If the train company has given advance warning of engineering works and altered the timetable you will not normally be entitled to compensation.

Virgin Trains gives this clarification:

When a specially-advertised revised timetable is in operation, for example at times of engineering work, we will be measured against the revised times.

Anecdotally some argument exists as to whether this is an absolute get-out clause, e.g. from a popular UK site discussing railway issues: http://www.railforums.co.uk/showthread.php?t=130857

http://www.railforums.co.uk/showthread.php?t=130857

Yesterday I travelled from St Pancras to Rainham by Southeastern. Due to engineering works the hourly morning train service was running to a special timetable with departures at xx55 rather than the xx25 in the normal timetable. As a result I wasted 30 minutes at St Pancras and arrived at Rainham 30 minutes later than I had expected.

Would this be claimable via delay repay?

No, a timetable change for planned engineering works is not a delay.

Alternatively: http://forums.moneysavingexpert.com/showthread.php?t=2979502

No not at all. Because of the nature of the bus replacement services then there is no case for a refund.

Again the delay repay is not applicable when there are engineering works in force

The appropriate advice would appear to be to study the precise conditions of carriage of your train operating company backed by the above additional information and claim for delay repay anyway. It can't hurt to claim.