You can install the version you need easily:
First get source:
$ wget https://ftp.gnu.org/gnu/automake/automake-1.15.tar.gz
Unpack it:
$ tar -xzvf automake-1.15.tar.gz
Build and install:
$ cd automake-1.15
$ ./configure --prefix=/opt/aclocal-1.15
$ make
$ sudo mkdir -p /opt
$ sudo make install
Use it:
$ export PATH=/opt/aclocal-1.15/bin:$PATH
$ aclocal --version
aclocal (GNU automake) 1.15
Now when aclocal is called, you get the right version.