Arbu,
When the idea of the trip first came up at the end of last year Hypocolius was one of my main potential targets. But it became clear that this was increasingly unlikely.
Below is what the uaebirding website has to say - the information is a bit out of date, as you can see, even the updates. I came to believe Lulu Island is the only potential place now and I didn't visit as I couldn't find details on how to get there.
"HYPOCOLIUS
An erratic and nomadic winter visitor in variable numbers. Can be found in any plantation in the country, with the formerly good (and very accessible) site of Ghantoot possibly still having birds, at least erratically. Since 2008 one farm on Sila'a Peninsula has proved a reliable wintering site, at least from late November until January (position 24.070195 , 51.774336).
The birds have also regularly wintered on the rarely-visited Dalma Island (in the forest near the hospital and big mosque). The difficult to access Lulu Island off Abu Dhabi has also proved a very reliable wintering site, but you will need your own boat to reach there.
A new roosting site was discovered in November 2012; the mangrove patch immediately to the east of Yas Island--Yas Links Golf Course (position 24.485080 , 54.589927).
F - Lulu Island
Unlike all the above sites, this one requires some effort to get to. However, this may prove very worthwhile indeed, as, also unlike all the above sites, Lulu Island has had Hypocolius wintering annually (since 2009 at least). These are present reliably from mid (sometimes early) November to late March, peaking in February – March when over 100 may occur. Views are often superb, especially early morning when the perch openly and can be scoped at leisure.
In general, the best area to look for Hypocolius is highlighted in red in the map above although, over many visits, groups have been seen at various parts of the island, particularly those marked in blue. Exact details, including how to get to Lulu Island, are presented at this link.
Although technically you are not allowed to walk in the island interior, being on the beach is generally ok, and nobody should bother you if stay on it. So you could walk along the beach up to the red area and then just cut in a little to check the best area – it is only a very short distance from the beach. Make sure you know the call – playing it back will not help but you nearly always hear the birds before you see them – there are freely available recordings, some of which came from Lulu Island, at this link.
Ghantoot used to be good for Grey Hypocolius in the plantation pictured below during late afternoons between November and mid April. This is no longer the case, as the plantation is no longer being watered."
I see from ebird that 25 were seen on Lulu Island on 4th February - perhaps I should have tried harder to get out there...