Does several PIC12F683 pull-ups cause short circuit
According to the datasheet for PIC12F683, the max pull-up current is 400μA (see D070 on p.121).  The 25 PICs pulling up together would pull 10mA.  

The nominal max GPIO sink current for this PIC is 8.5mA (see D080 on p.121), while the absolute max is 25mA.  There is also a more detailed chart fig.16-24 on p.149, which goes to 10mA.

You can make do [without a comfortable margin] using only internal pull-ups and not exceeding max sink current for a GPIO pin.  But I would use external pull-up resistors in this case.