I was to have gone on holiday with Amy,but she couldn't get time off work是否等於I was supposed to go on holiday with Amy,but she couldn't get ~?

( 這是出現於BBC Learning English 的例句)
http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/learnitv327.shtml
I was to have gone on holiday with Amy, but she couldn't get time off work.
I was supposed to go on holiday with Amy, but she couldn't get time off work.

基本上，意思是相近，也許多至80%，視情況而定。中英文都一樣，沒有完全相同的同義詞，用詞不同，結構不同的句子，意義上都有點差異。
be to V 通常指正式的安排 (已確定的行程計劃)
be supposed to 則有 "期望，預期"，但含有未確定的意思。

If (to have gone=be to V=clear=not doubt), then(be supposed to=required to=let it be thought).
suppose vt.
I suppose Amy can't go...
I don't suppose that Amy can go...
I'm not supposed to go on holiday with Amy who has no time off supposedly (adv).
Let me suppose that Amy can't get the time off.
Amy is supposed to get no time off.
Amy wouldn't get the time off, I suppose.

這句用was to have + p.p 表示主觀意思肯定要去，如was to be 則有8成以上會去，但I am supposed to 則去的機率不高。所以两句意思一樣，但主觀認定不同。be to +V 表未來式。