While I can't answer the question in the OP, I'd like to dispute the veracity of the Wikipedia article. The British Army only brought five radio sets to the Boer War in 1899. These failed to work as well as advertised, and were withdrawn from service. Instead, all five were fitted to five Royal Navy cruisers, which operated in the blockade of South Africa. The Boers had ordered six radio sets from Siemens, but these were intercepted by the British, and cannibalised to support the British systems. The Boers had neither their own systems, nor captured British systems, with which to intercept British radio systems. The source quoted by Wikipedia doesn't even support the assertions made in the article - the quote is

As early as 1900 in the Boer War, the Royal Navy in South Africa appears to have used wireless sets inherited from the Royal Engineers to signal from the neutral port of Lourenço Marques “information relative to the enemy” albeit in violation of international law. [71] This first use of radio for intelligence purposes depended, of course, on the inability of others to intercept the signals, but in 1900, only the British in that part of the world had any wireless capability.

(RADIO SPIES — EPISODES IN THE ETHER WARS, Bartholomew Lee, 15 ANTIQUE WIRELESS ASSOCIATION REVIEW, 2002)

As the quote states, nobody was intercepting the signals sent by the British, because only they had radio systems. The claim the source supports is that the British were sending sensitive messages over radio during the Boer War.

I believe it was a fairly trivial task to tap into a telegraph system, but the usefulness of such a tactic would be severely limited. One would have to monitor full time to catch an important message amongst the vast chaff of requisitions, casualty reports, and all the dross of everyday communications. Then, one would have to figure out which cypher was used, decode it, and whether 'orange' meant Richmond or Pittsburgh.

this is an interesting article about it.