AMS-LHR,
no, no 'grand tours' of Terminal 5 have taken place for cabin crew. only for heathrow customer service staff (ground staff in the terminals).
and, as far as i can tell, there won't be. it would be a logistical nightmare. having to off-line 13,000 LHR based cabin crew for a day for a terminal familiarisation isn't something that i'm sure that the company is keen to do - what with all the operational difficulties that we've been through recently, and i'm sure of which there is more to come before next spring.
however, you may get a look around on your course. although i'm not aware of this happening so far. you'll be on your course when BAA hand the keys for T5 over to BA in early/mid september, so things might change for new entrant courses.
however, as far as i'm aware, we will all be getting a DVD familiarisation package of T5 fairly soon.