No it is not possible.
A croc is not guaranteed I'm afraid, as has been mentioned on this group in the recent past, but as a reminder, here is a heads up regarding RhB Croc (Ge6/6I) workings:
Essentially, none are guaranteed.
Firstly it is worth remembering that since the demise of 412 10 years ago, there are only two operable Crocs surviving to choose from and they are old, high maintenance machines and are indeed pulled out for maintenance quite regularly. The latest list suggests 415 may be sidelined for some time, leaving only 414 in use, as 415 was listed as 'out of service for revision' as at 12 June 2018
And a personal experience from last August (2017), a Croc turn that was officially re-advertised by RhB as Ge4/4I due to the aforementioned regular maintenance of the Croc actually turned up as a Ge6/6II
Beware also the subtleties of the diagramming and advertising, viz:
The Albula Experience train website blurb does not specifically mention Croc haulage (only the 'library picture' shows a Croc).
The new Davos - Filisur regular trains are like a 'plandampf' - and the Croc is (theoretically) booked - Turn 901 in the RhB loco diagrams (though again, the diagrams show 'Historische Lok' not specifically Croc).
The Albula Experience seems to be categorised as a 'special' so not shown in the loco diagrams, hence the possibility of any loco being put out.