How long it takes for big publishing houses to evaluate a book proposal?

The evaluation process is long and depends on several factors. How many editors the publishing house has, did you query correctly (this helps a lot, so contact them via phone or check their website to see what they request upon submission), etc.

Like Anayat Bukhari said, there is no one set timing. My suggestion is to follow up either by email or phone10-14 days after you send in your manuscript. One key point to remember is that we as publishers are in contact with each other so you don’t want to seem like a compulsive spammer so don’t overdo the email follow up. This way the publisher will give you a theoretical timeframe. Keep in mind if you send submissions the couple of months before a book fair (national, LBF, FBF, BEA, etc.) it will take longer for a publisher to get back to you because they would be preparing for the fair and most people responsible for reviewing your book would be travelling or busy.

Also consider submitting your manuscript to more than one publisher, but keep a significant buffer period (approximately2 weeks) between each submission. 

It extremely varies as some may do it in weeks, others in months and yet others may take more than a year.