Both Jubilee and Greenford are safe as you can be in the present climate. Jubilee now has the biggest inward operation in the country it has Guildford , Kingston , Twickenham and South West London. To close Jubilee you would have to find a mail centre which could handle that. Greenford is already up to capacity on the inward as it took in W2- 14 in January and is struggling to cope with that additonal inward.
In additon for an outer London weighting mail centre is has good cost per item productivity. It is also a lease and based on the current concept of a one floor mail centre.
The majority of the mail centres which were earmarked for closure were the old multi floor mail centred which have been moved to bigger mail centres or new builds. A few have closed due to IR problems Liverpool , Oxford and East London which was a new build were all closed by Royal Mail due to IR problems.