First, there was no pact, Ireland didn't agree to it, so the rest can get that 15% and stick it where it belongs.
Second it not about every country having the same tax as Ireland but more on Ireland raising its tax to other countries levels.
Ireland is a member of the European Union, so I don't think that Germany or any other EU nation can impose a "special tax" on imports from that country. That will go against one of the basic principles of the European Union. The desperation from the part of governments is understandable. Revenues are not increasing at a rate as per the expectation of the government. With every passing year, the general population is demanding more and more freebies. The income taxes are already sky high in countries such as Germany (up to 60% in some cases) and the VAT is also one of the highest in the world. Now the only option is to find new avenues, such as corporate tax.