Yes they are so good at mimicry that if they are in the presence of other birds they'll pick up the other birds' speech and vocalizations. I've heard of budgies who were housed next to finches and the budgie sounded like the finches
Jerry picked up English and cockatiel when he was home with us for awhile. When we brought Winston home I had nearly forgotten what the true budgie sounds are like! And their songs and warbles can differ too (I think I've read that in the wild they choose mates based on their song - as one criteria - and are more likely to choose a mate with a similar sounding song). Now Winston has picked up cockatiel-speak, a little bit of English, and they've blended their budgie sounds together
