If a person forgot to recite Birkot Ha'Torah in the morning before Shaharit, and he realizes his mistake only after Shaharit, he does not recite Birkot Ha'Torah, as this obligation was satisfied through the recitation of Ahabat Olam – the Beracha recited immediately before Shema. In Ahabat Olam, we pray to G-d to grant us the ability to properly learn and practice the Torah – which is also the theme of Birkot Ha'Torah, and therefore, one who had not recited Birkot Ha'Torah fulfills this obligation through the recitation of Ahabat Olam.
Halacha requires reading some Torah text immediately after reciting Birkot Ha'Torah, which is why we customarily read the verses of Birkat Kohanim right after Birkot Ha'Torah. If one fulfills the Birkot Ha'Torah obligation through the recitation of Ahabat Olam, he obviously cannot read the verses of Birkat Kohanim right after Ahabat Olam, as this would constitute a Hefsek (forbidden interruption) in the prayer service. And the reading of Shema after Ahabat Olam does not satisfy this requirement, because we read Shema not for the sake of Torah learning, but as part of the prayer service. Therefore, one who fulfills his Birkot Ha'Torah obligation through the recitation of Ahabat Olam should read some verses – such as the verses of Birkat Kohanim – immediately after the Amida prayer.
The accepted Halacha is that the recitation of Ahabat Olam fulfills the obligation of Birkot Ha'Torah even if one did not have in mind to fulfill the obligation through this recitation. Although there were those who claimed that this works only with Kavana – intention to fulfill one's obligation – the consensus among the Poskim is that reciting Ahabat Olam suffices to fulfill the Birkot Ha'Torah obligation even without this intention. This is the ruling of Hacham Ovadia Yosef.
The Peri Megadim (Rav Yosef Ben Meir Teomim, 1727-1792) addresses the case of a person who arrived in the synagogue late, and decided to skip the morning blessings so he can try to catch up to the congregation. If, the Peri Megadim writes, this person prefers to recite the actual text of Birkot Ha'Torah, rather than fulfill this obligation through the recitation of Ahabat Olam, he may have specific intention not to fulfill this requirement when reciting Ahabat Olam. This intention prevents Ahabat Olam from satisfying the obligation, and so the individual may then recite the regular text of Birkot Ha'Torah after the Amida.
Hacham Ovadia Yosef disagrees with this ruling of the Peri Megadim. He argues that having such intention would cause a "Beracha She'ena Sericha" – an unnecessary Beracha. Halacha does not allow purposely arranging a situation that necessitates a blessing that would otherwise not be needed. Therefore, if one has the possibility of fulfilling his Birkot Ha'Torah obligation through the recitation of Ahabat Olam, then he cannot choose not to so he can then recite the actual Birkot Ha'Torah.
A variation of the Ahabat Olam blessing which we recite in the morning is recited during Arbit, also right before Shema. This evening blessing, too, is effective in satisfying the Birkot Ha'Torah requirement in a situation where one is required to recite Birkot Ha'Torah at night. This happens when a person takes a nap during the evening, after dark – when he wakes up, he must recite Birkot Ha'Torah. But if he had not recited Arbit before he went to sleep, then he should instead fulfill his obligation through the recitation of Ahabat Olam during Arbit. An example of such a case is a person who comes home from work after dark, takes a nap, and then wakes up and goes to the synagogue for Arbit and a Torah class. He does not recite Birkot Ha'Torah before his class, because he fulfills his requirement through the recitation of Ahabat Olam.
Summary: If a person did not recite Birkot Ha'Torah in the morning before Shaharit, and he realizes his mistake after Shaharit, he does not recite Birkot Ha'Torah, as he fulfilled his obligation through the recitation of Ahabat Olam before Shema, even without intending to do so. If the person realized his mistake before reciting Ahabat Olam, he should fulfill his Birkot Ha'Torah obligation through the recitation of Ahabat Olam; he should not have intention not to fulfill the requirement with Ahabat Olam so he can recite Birkot Ha'Torah later. If a person takes a nap during the evening, after dark, he must recite Birkot Ha'Torah before learning Torah when he wakes up, but if he had yet to recite Arbit, then he does not recite Birkot Ha'Torah, as he instead fulfills his obligation through the recitation of Ahabat Olam before Shema during Arbit.