parent::initContent();

$categories = Category::getRootCategory()->recurseLiteCategTree();
foreach ($categories['children'] as &$children)
{
    $products = Product::getProducts($this->context->language->id, 0, 0, 'date_add', 'ASC', $children['id']);
    foreach($products as $product)
        $children['products'][$product['id_product']] = $product['name'];
}

$this->context->smarty->assign('categories', $categories);

<div class="categTree">
    <h3>Товары</h3>
    <div class="tree_top"><a href="{$base_dir_ssl}" title="{$categories.name|escape:'htmlall':'UTF-8'}">{$categories.name|escape:'htmlall':'UTF-8'}</a></div>
    <ul class="tree">
    {if isset($categories.children)}
        {foreach $categories.children as $child}
        <li {if $child@last}class="last"{/if}>
            <a href="{$child.link|escape:'htmlall':'UTF-8'}" title="{$child.desc|escape:'htmlall':'UTF-8'}">{$child.name|escape:'htmlall':'UTF-8'}</a>
            {if isset($child.products)}
            <ul class="tree">
                {foreach $child.products as $id => $product_name}
                <li {if $child@last}class="last"{/if}>
                    <a href="{$link->getProductLink($id)}">{$product_name|escape:'htmlall':'UTF-8'}</a>
                </li>
                {/foreach}
            </ul>
            {/if}
        </li>
        {/foreach}
    {/if}
    </ul>
</div>

$products = Product::getProducts($this->context->language->id, 0, 0, 'date_add', 'ASC', $children['id']);

$products = Product::getProducts($this->context->language->id, 0, 0, 'date_add', 'ASC', $children['id'], true);