So, I create a little repo with a single Java file in it and branched it. Let's assume the file is like this:
1: Line1 2: Line2 3: Line3 4: xxx NIE yyy 5: Line5 6: Line6 7: Line7
On the trunk, I have changed NIE to TAK and Line2 to XXX and committed the change. On the the branch, I have changed NIE to TAK and Line6 to YYY and committed the change as well. When I merged the changes in trunk into the working copy of the branch, I've got only a change of Line2 brought in.
So, the conclusion is, that an identical change is merged by SVN smoothly, even if other non-matching changes were found nearby. Or possibly, it's not SVN but the merge tool, which in my case was the Tortoise SVN built in merge tool.